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  • 1. Andreyev, A. N.
    et al.
    Huyse, M.
    Van Duppen, P.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Antalic, S.
    Ackermann, D.
    Franchoo, S.
    Heßberger, F. P.
    Hofmann, S.
    Kojouharov, I.
    Kindler, B.
    Kuusiniemi, P.
    Lesher, S. R.
    Lommel, B.
    Mann, R.
    Nishio, K.
    Page, R. D.
    Streicher, B.
    Šáro, Š.
    Sulignano, B.
    Wiseman, D.
    Wyss, Ramon A .
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Signatures of the Z=82 shell closure in alpha-decay process2013In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 24, article id 242502Article in journal (Refereed)
    Abstract [en]

    In recent experiments at the velocity filter Separator for Heavy Ion reaction Products (SHIP) (GSI, Darmstadt), an extended and improved set of α-decay data for more than 20 of the most neutron-deficient isotopes in the region from lead to thorium was obtained. The combined analysis of this newly available α-decay data, of which the Po186 decay is reported here, allowed us for the first time to clearly show that crossing the Z=82 shell to higher proton numbers strongly accelerates the α decay. From the experimental data, the α-particle formation probabilities are deduced following the Universal Decay Law approach. The formation probabilities are discussed in the framework of the pairing force acting among the protons and the neutrons forming the α particle. A striking resemblance between the phenomenological pairing gap deduced from experimental binding energies and the formation probabilities is noted. These findings support the conjecture that both the N=126 and Z=82 shell closures strongly influence the α-formation probability.

  • 2.
    Bäck, Torbjörn
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ghazi Moradi, Farnaz
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wadsworth, R.
    Transition probabilities near Sn-100 and the stability of the N, Z=50 shell closure2013In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 87, no 3, p. 031306-Article in journal (Refereed)
    Abstract [en]

    Recent B(E2; 0(g.s.)(+) -> 2(1)(+)) measurements in light tin isotopes have revealed surprisingly large values relative to standard shell model predictions, generating an unexpected asymmetry in the B(E2) values with respect to the neutron midshell. This effect has triggered various speculations as to its origin, such as a possible weakening of the N, Z = 50 shell closure. Here we present new shell model calculations to investigate the origin of the observed asymmetric character of the B(E2) values in the tin isotopes. By including the effects of the neutron g(9/2) orbital below the N = 50 shell gap it is shown that Pauli blocking effects may play an important role near the N = 50 shell closure. A new set of single-particle energies and monopole interactions, fitted to the experimental data in the region, together with the isospin-dependent effective charge suggested by Bohr and Mottelson is shown to reproduce the experimental transition rate values in the Sn isotopic chain.

  • 3.
    Bäck, Torbjörn
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Moradi, Farnaz Ghazi
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wadsworth, R.
    The B(E2;0(gs)(+) -> 2(+)) systematics of Sn and Te isotopes in light of data in the light Sn region including a recent measurement in Te-108 using the combined recoil-decay-tagging-recoil-distance Doppler technique2012In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T150, p. 014003-Article in journal (Refereed)
    Abstract [en]

    An experimental technique combining the well-established alpha/p-decay-recoil-tagging method with a differential plunger has recently been successful in producing results in the neutron-deficient region near Sn-100. This experimental technique is briefly presented here and the result of a recent measurement for Te-108 is put in the context of the systematics of B(E-2) values for the Te and Sn isotopic chains. New state-of-the-art shell-model calculations are presented for the Sn data, and possible explanations for the unusually large B(E-2) values for the Sn isotopes near the N = 50 shell closure are given.

  • 4.
    Bäck, Torbjörn
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ghazi Moradi, Farnaz
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Al-Azri, H.
    Bloor, D.
    Brock, T.
    Wadsworth, R.
    Grahn, T.
    Greenlees, P. T.
    Hauschild, K.
    Herzan, A.
    Jacobsson, U.
    Jones, P. M.
    Julin, R.
    Juutinen, S.
    Ketelhut, S.
    Leino, M.
    Lopez-Martens, A.
    Nieminen, P.
    Peura, P.
    Rahkila, P.
    Rinta-Antila, S.
    Ruotsalainen, P.
    Sandzelius, M.
    Saren, J.
    Scholey, C.
    Sorri, J.
    Uusitalo, J.
    Go, S.
    Ideguchi, E.
    Cullen, D. M.
    Procter, M. G.
    Braunroth, T.
    Dewald, A.
    Fransen, C.
    Hackstein, M.
    Litzinger, J.
    Rother, W.
    Lifetime measurement of the first excited 2(+) state in (108)Te2011In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 84, no 4, p. 041306-Article in journal (Refereed)
    Abstract [en]

    The lifetime of the first excited 2(+) state in the neutron deficient nuclide (108)Te has been measured for the first time, using a combined recoil decay tagging and recoil distance Doppler shift technique. The deduced reduced transition probability is B(E2;0(g.s.)(+) -> 2(+)) = 0.39(-0.04)(+0.05)e(2)b(2). Compared to previous experimental data on neutron deficient tellurium isotopes, the new data point constitutes a large step (six neutrons) toward the N = 50 shell closure. In contrast to what has earlier been reported for the light tin isotopes, our result for tellurium does not show any enhanced transition probability with respect to the theoretical predictions and the tellurium systematics including the new data is successfully reproduced by state-of-the-art shell model calculations.

  • 5. Carroll, R. J.
    et al.
    Hadinia, Baharak
    KTH, School of Engineering Sciences (SCI), Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics.
    Joss, D. T.
    Page, R. D.
    Uusitalo, J.
    Andgren, K.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics.
    Darby, I. G.
    Eeckhaudt, S.
    Grahn, T.
    Gray-Jones, C.
    Greenlees, P. T.
    Jones, P. M.
    Julin, R.
    Juutinen, S.
    Leino, M.
    Leppanen, A. -P
    Nyman, M.
    Pakarinen, J.
    Rahkila, P.
    Sandzelius, Mikael
    KTH, School of Engineering Sciences (SCI), Physics.
    Saren, J.
    Scholey, C.
    Seweryniak, D.
    Simpson, J.
    Multiparticle configurations of excited states in Lu-1552016In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 94, no 6, article id 064311Article in journal (Refereed)
    Abstract [en]

    Excited states in the neutron-deficient N = 84 nuclide Lu-155 have been populated by using the Pd-102(Ni-58, alpha p) reaction. The Lu-155 nuclei were separated by using the gas-filled recoil ion transport unit (RITU) separator and implanted into the Si detectors of the gamma recoil electron alpha tagging (GREAT) spectrometer. Prompt gamma-ray emissions measured at the target position using the JUROGAM Ge detector array were assigned to Lu-155 through correlations with alpha decays measured in GREAT. Structures feeding the (11/2(-)) and (25/2(-)) alpha-decaying states have been revised and extended. Shell-model calculations have been performed and are found to reproduce the excitation energies of several of the low-lying states observed to within an average of 71 keV. In particular, the seniority inversion of the 25/2(-) and 27/2(-) states is reproduced.

  • 6.
    Cederwall, Bo
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ghazi Moradi, Farnaz
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Blomqvist, Jan-Erik
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Clément, E.
    Grand Accélérateur National d´lons Lourds, Cean Cedex, France.
    de France, G.
    Grand Accélérateur National d´lons Lourds, Cean Cedex, France.
    Wadsworth, R.
    Department of Physics, University of York, UK.
    Andgren, Karin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Lagergren, Karin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Dijon, A.
    Grand Accélérateur National d´lons Lourds, Cean Cedex, France.
    Jaworski, G.
    Heavy Ion Laboratory, Univeristy of Warsaw, Warsaw, Poland.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Nyakó, B. M.
    Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary.
    Nyberg, J.
    Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Palacz, M.
    Heavy Ion Laboratory, Univeristy of Warsaw, Warsaw, Poland.
    Al-Azri, H.
    Department of Physics, University of York, UK.
    Algora, A.
    IFIC, CSIC University of Valencia, Valencia, Spain.
    de Angelis, G.
    Instituto Nazionael di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro, Italy.
    Atac, Ayse
    KTH, School of Engineering Sciences (SCI).
    Bhattacharyya, S.
    Grand Accélérateur National d´lons Lourds, Cean Cedex, France.
    Brock, T.
    Department of Physics, University of York, York, UK.
    Brown, J. R.
    Department of Physics, University of York, York, UK.
    Davies, P.
    Department of Physics, University of York, York, UK.
    Di Nitto, A.
    Dipartimento di Scienze Fisiche, Universitá di Napoli and Instituto Nazionale di Fisica Nucleare, Napoli, Italy.
    Dombrádi, Zs.
    Institute of Nuclear Research of the Hungarian Academy of Science, Debrecen, Hungary.
    Gadea, A.
    IFIC, CSIC, University of Valencia, Valencia, Spain.
    Gál, J.
    Institute of Nuclear Research of the Hungarian Academy of Science, Debrecen, Hungary.
    Hadinia, Baharak
    KTH, School of Engineering Sciences (SCI), Physics.
    Johnston-Theasby, F.
    Department of Physics, University of York, York, UK.
    Joshi, P.
    Department of Physics, University of York, York, UK.
    Juhász, K.
    Department of Information Technology, Universty of Debrecen, Debrecen, Hungary.
    Julin, R.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Jungclaus, A.
    Instituto de Estructura de la Materia, Madrid, Spain .
    Kalinka, G.
    Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary.
    Kara, S. O.
    Department of Physics, Ankara University, Tandogan Ankarar, Turkey.
    Khaplanov, Anton
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Kownacki, J.
    Heavy Ion Laboratory, Universty of Warsaw, Warsaw, Poland.
    La Rana, G.
    Dipartimento di Scienze Fisiche, Universitá di Napoli and Instituto Nazionale di Fisica Nucleare, Napoli, Italy.
    Lenzi, S. M.
    Dipartimento di Fisica dell'Universitá di Padova and Instituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova, Italy.
    Molnár, J.
    Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary.
    Moro, R.
    Dipartimento di Scienze Fisiche, Universitá di Napoli and Instituto Nazionale di Fisica Nucleare, Napoli, Italy.
    Napoli, D. R.
    Instituto Nazionale di Fisica Nucleare, Laboratori Natzionali di Legnaro, Legnaro, Italy.
    Nara Singh, B. S.
    Department of Physics, University of York, York, UK.
    Persson, Andreas
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Recchia, F.
    Dipartimento di Fisica dell'Universitá di Padova and Instituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova, Italy.
    Sandzelius, Mikael
    KTH, School of Engineering Sciences (SCI), Physics.
    Scheurer, J. -N
    Université Bordeaux, Centre d'Etudes Nucléaires de Bordeaux Gradignan, Gradignan, France.
    Sletten, G.
    The Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
    Sohler, D.
    Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary.
    Söderström, P. -A
    Department of Physics and Astromony, Uppsala University, Uppsala, Sweden.
    Taylor, M. J.
    Department of Physics, University of York, York, UK.
    Timár, J.
    Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Hungary.
    Valiente-Dobón, J. J.
    instituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro, Italy.
    Vardaci, E.
    Dipartimento di Scienze Fisiche, Universitá di Napoli and Instituto Nazionale di Fisica Nucleare, Napoli, Italy.
    Williams, S.
    TRIUMF, Vancouver, British Columbia, Canada.
    Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd2011In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 469, no 7328, p. 68-71Article in journal (Refereed)
    Abstract [en]

    Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work(1) that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing(2-6), in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus Pd-92. Gamma rays emitted following the Ni-58(Ar-36,2n)Pd-92 fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution c-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction(2-6). We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling(7,8)) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

  • 7.
    Changizi, Sara A.
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Empirical pairing gaps, shell effects, and di-neutron spatial correlation in neutron-rich nuclei2015In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 940, p. 210-226Article in journal (Refereed)
    Abstract [en]

    The empirical pairing gaps derived from four different odd-even mass staggering formulas are compared. By performing single-j shell and multi-shell seniority model calculations as well as by using the standard HFB approach with Skyrme force we show that the simplest three-point formula δC(3)(N)=12[B(N,Z)+B(N-2,Z)-2B(N-1,Z)] can provide a good measure of the neutron pairing gap in even-N nuclei. It removes to a large extent the contribution from the nuclear mean field as well as contributions from shell structure details. It is also less contaminated by the Wigner effect for nuclei around N=Z. We also show that the strength of δC(3)(N) can serve as a good indication of the two-particle spatial correlation in the nucleus of concern and that the weakening of δC(3)(N) in some neutron-rich nuclei indicates that the di-neutron correlation itself is weak in these nuclei.

  • 8.
    Changizi, Sara A.
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics.
    Density dependence of the pairing interaction and pairing correlation in unstable nuclei2015In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 91, no 2, article id 024305Article in journal (Refereed)
    Abstract [en]

    This work aims at a global assessment of the effect of the density dependence of the zero-range pairing interaction. Systematic Skyrme-Hartree-Fock-Bogoliubov calculations with the volume, surface, and mixed pairing forces are carried out to study the pairing gaps in even-even nuclei over the whole nuclear chart. Calculations are also done in coordinate representation for unstable semimagic even-even nuclei. The calculated pairing gaps are compared with empirical values from four different odd-even staggering formulas. Calculations with the three pairing interactions are comparable for most nuclei close to the beta-stability line. However, the surface interaction calculations predict neutron pairing gaps in neutron-rich nuclei that are significantly stronger than those given by themixed and volume pairing. On the other hand, calculations with volume andmixed pairing forces show noticeable reduction of neutron pairing gaps in nuclei far from stability.

  • 9.
    Changizi, Sara A.
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Odd-even staggering in neutron drip line nuclei2016In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 951, p. 97-115Article in journal (Refereed)
    Abstract [en]

    We have done systematic Hartree-Fock-Bogoliubov calculations in coordinate space on the one-quasi-particle energies and binding energy odd-even staggering (OES) in semi-magic nuclei with the zero-range volume, mixed and surface pairing forces in order to explore the influence of their density dependence. The odd-N isotopes are calculated within the blocking scheme. The strengths for the pairing forces are determined in two schemes by fitting locally to reproduce pairing gap in 120Sn and globally to all available data on the OES of semi-magic nuclei with Z≥8. In the former calculations, there is a noticeable difference between the neutron mean gaps in neutron-rich O, Ca, Ni and Sn isotopes calculated with the surface pairing and those with the mixed and volume pairing. The difference gets much smaller if the globally optimized pairing strengths are employed. The heavier Pb isotopes show the opposite trend. Moreover, large differences between the mean gap and the OES may be expected in both calculations when one goes towards the neutron drip line.

  • 10. Cheng, Y. Y.
    et al.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Zhao, Y. M.
    Arima, A.
    Nucleon-pair states of even-even Sn isotopes based on realistic effective interactions2016In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 94, no 2, article id 024321Article in journal (Refereed)
    Abstract [en]

    In this paper we study yrast states of Sn-128,Sn-126,Sn-124 and Sn-104,Sn-106,Sn-108 by using the monopole-optimized realistic interactions in terms of both the shell model (SM) and the nucleon-pair approximation (NPA). For yrast states of Sn-128,Sn-126 and Sn-104,Sn-106, we calculate the overlaps between the wave functions obtained in the full SM space and those obtained in the truncated NPA space, and find that most of these overlaps are very close to 1. Very interestingly, for most of these states with positive parity and even spin or with negative parity and odd spin, the SM wave function is found to be well represented by one nucleon-pair basis state, viz., a simple picture of "nucleon-pair states" (nucleon-pair configuration without mixings) emerges. In Sn-128,Sn-126, the positive-parity (or negative-parity) yrast states with spin J > 10 (or J > 7) are found to be well described by breaking one or two S pairs in the 10(1)(+) (or 7(1)(-)) state, i.e., the yrast state of seniority-two, spin-maximum, and positive-parity (or negative-parity), into non-S pair(s). Similar regularity is also pointed out for Sn-104,Sn-106. The evolution of E2 transition rates between low-lying states in Sn-128,Sn-126,Sn-124 is discussed in terms of the seniority scheme.

  • 11. Delion, D. S.
    et al.
    Liotta, R. J.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon A.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Probing shape coexistence by alpha decays to 0(+) states2014In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 90, no 6, p. 061303-Article in journal (Refereed)
    Abstract [en]

    We analyze the alpha-decay fine structure to excited 0(2)(+) states in Hg and Rn isotopes. These states are described as minima in the potential energy surface (PES) provided by the standard deformed Woods-Saxon plus pairing approach. We also investigate alpha decay from the excited state P(0(2)(+)) in the parent nucleus by evaluating the corresponding hindrance factor (HF). By analyzing the experimental HF's we find the remarkable property that the ground and excited states D(0(1)(+)) and D(0(2)(+)) in the daughter nuclei are occupied with almost equal probabilities if there is no excited P(0(+)) states in the parent nucleus. Moreover, if there exists an excited state P(0(2)(+)) then the occupation probability of this state is 25%.

  • 12. Doncel, Maria
    et al.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics.
    Cullen, D. M.
    Hodge, D.
    Qi, Chong
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Taylor, M. J.
    Procter, M.
    Auranen, K.
    Grahn, T.
    Greenlees, P. T.
    Jakobsson, U.
    Julin, R.
    Juutinen, S.
    Herzan, A.
    Konki, J.
    Leino, M.
    Pakarinen, J.
    Partanen, J.
    Peura, P.
    Rahkila, P.
    Ruotsalainen, P.
    Sandzelius, M.
    Saren, J.
    Scholey, C.
    Sorri, J.
    Stolze, S.
    Uusitalo, J.
    Lifetime measurement of the first excited 2(+) state in Te-1122015In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 91, no 6, article id 061304Article in journal (Refereed)
    Abstract [en]

    The lifetime of the 2(+) --> 0(g.s.)(+) transition in the neutron-deficicient nucleus Te-112 has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is B(E2 :0(g.s.)(+) --> 2(+)) = 0.46 +/- 0.04 e(2)b(2), indicating that there is no unexpected enhancement of the B(E2 :0(g.s.)(+) --> 2(+)) values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations.

  • 13.
    Doncel, Maria
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics.
    Li, Hongjie J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Jakobsson, Ulrika
    KTH, School of Engineering Sciences (SCI), Physics.
    Auranen, K.
    Boenig, S.
    Drummond, M. C.
    Grahn, T.
    Greenlees, P. T.
    Herzan, A.
    Joss, D. T.
    Julin, R.
    Juutinen, S.
    Konki, J.
    Kroell, T.
    Leino, M.
    McPeake, C.
    O'Donnell, D.
    Page, R. D.
    Pakarinen, J.
    Partanen, J.
    Peura, P.
    Rahkila, P.
    Ruotsalainen, P.
    Sandzelius, M.
    Saren, J.
    Saygi, B.
    Scholey, C.
    Sorri, J.
    Stolze, S.
    Taylor, M. J.
    Thornthwaite, A.
    Uusitalo, J.
    Lifetime measurements of excited states in W-162 and W-164 and the evolution of collectivity in rare-earth nuclei2017In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 95, no 4, article id 044321Article in journal (Refereed)
    Abstract [en]

    Lifetimes of the first excited 2(+) states in the extremely neutron- deficient W-162 and W-164 nuclei have been measured using the recoil distance Doppler shift technique. Experimental B(E2) data for the isotopic chains of hafnium, tungsten, and osmium, from the midshell region near the beta-stability line towards the N = 82 closed shell and the most neutron-deficient nuclides, are compared with predictions of nuclear deformations and 2(1)(+) -> 0(g.s)(.+) reduced transition strengths from different classes of state-of-the-art theoretical model calculations. The results reveal striking differences and deficiencies in the predictive power of current nuclear structure models.

  • 14.
    Ertoprak, Aysegul
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Doncel, Maria
    KTH, School of Engineering Sciences (SCI), Physics.
    Jakobsson, U.
    Royal Inst Technol KTH, Dept Phys, SE-10691 Stockholm, Sweden.;Univ Helsinki, Dept Chem, POB 3, FIN-00014 Helsinki, Finland..
    Nyako, B. M.
    MTA Atomki, H-4001 Debrecen, Hungary..
    Jaworski, G.
    Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Legnaro, Italy..
    Davies, P.
    Univ York, Dept Phys, York YO10 5DD, N Yorkshire, England..
    de France, G.
    CEA DSM CNRS IN2P3, GANIL, Bd Henri Becquerel,BP 55027, F-14076 Caen 5, France..
    Kuti, I.
    MTA Atomki, H-4001 Debrecen, Hungary..
    Napoli, D. R.
    Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Legnaro, Italy..
    Wadsworth, R.
    Univ York, Dept Phys, York YO10 5DD, N Yorkshire, England..
    Ghugre, S. S.
    UGC DAE Consortium Sci Res, Kolkata Ctr, Kolkata 700098, India..
    Raut, R.
    UGC DAE Consortium Sci Res, Kolkata Ctr, Kolkata 700098, India..
    Akkus, B.
    Istanbul Univ, Fac Sci, Dept Phys, TR-34134 Istanbul, Turkey..
    Al Azri, H.
    Univ York, Dept Phys, York YO10 5DD, N Yorkshire, England..
    Algora, A.
    MTA Atomki, H-4001 Debrecen, Hungary.;Univ Valencia, CSIC, Inst Fis Corpuscular, E-46980 Valencia, Spain..
    de Angelis, G.
    Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Legnaro, Italy..
    Atac Nyberg, Ayse
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics. Royal Inst Technol KTH, Dept Phys, SE-10691 Stockholm, Sweden..
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Boso, A.
    Univ Padua, Dipartimento Fis & Astron, Padua, Italy..
    Clement, E.
    CEA DSM CNRS IN2P3, GANIL, Bd Henri Becquerel,BP 55027, F-14076 Caen 5, France..
    Debenham, D. M.
    Univ York, Dept Phys, York YO10 5DD, N Yorkshire, England..
    Dombradi, Zs.
    MTA Atomki, H-4001 Debrecen, Hungary..
    Erturk, S.
    Nigde Omer Halisdemir Univ, Sci & Art Fac, Dept Phys, TR-51200 Nigde, Turkey..
    Gadea, A.
    Univ Valencia, CSIC, Inst Fis Corpuscular, E-46980 Valencia, Spain..
    Moradi, F. Ghazi
    Royal Inst Technol KTH, Dept Phys, SE-10691 Stockholm, Sweden..
    Gottardo, A.
    Univ Paris Saclay, CNRS IN2P3, Ctr Sci Nucl & Sci Mat, F-91405 Orsay, France..
    Huyuk, T.
    Univ Valencia, CSIC, Inst Fis Corpuscular, E-46980 Valencia, Spain..
    Ideguchi, E.
    Osaka Univ, Nucl Phys Res Ctr, Osaka, Japan..
    Li, H.
    Royal Inst Technol KTH, Dept Phys, SE-10691 Stockholm, Sweden..
    Michelagnoli, C.
    CEA DSM CNRS IN2P3, GANIL, Bd Henri Becquerel,BP 55027, F-14076 Caen 5, France..
    Modamio, V.
    Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Legnaro, Italy..
    Nyberg, J.
    Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Palacz, M.
    Univ Warsaw, Heavy Ion Lab, Pasteura 5A, PL-02093 Warsaw, Poland..
    Petrache, C. M.
    Univ Paris Saclay, CNRS IN2P3, Ctr Sci Nucl & Sci Mat, F-91405 Orsay, France..
    Recchia, F.
    Univ Padua, Dipartimento Fis & Astron, Padua, Italy..
    Sandzelius, M.
    Univ Jyvaskyla, Dept Phys, FI-40014 Jyvaskyla, Finland..
    Siciliano, M.
    Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Legnaro, Italy..
    Timar, J.
    MTA Atomki, H-4001 Debrecen, Hungary..
    Valiente-Dobon, J. J.
    Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Legnaro, Italy..
    Xiao, Z. G.
    Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China..
    M1 and E2 transition rates from core-excited states in semi-magic Ru-942018In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 54, no 9, article id 145Article in journal (Refereed)
    Abstract [en]

    Lifetimes of high-spin states have been measured in the semi-magic (N = 50) nucleus Ru-94. Excited states in Ru-94 were populated in the Ni-58(Ca-40, 4p)Ru-94* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from gamma-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm(2) metallic Ni-58 target. In total eight excited-state lifetimes in the angular momentum range I = (13-20)h have been measured, five of which were determined for the first time. The corresponding B(M1) and B(E2) reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

  • 15.
    Ertoprak, Aysegul
    et al.
    KTH, School of Engineering Sciences (SCI), Physics. Istanbul University Vezneciler/Fatih, Istanbul, Turkey.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Doncel, Maria
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Jakobsson, U.
    Nyako, B. M.
    Jaworski, G
    Davies, P.
    De France, G.
    Kuti, I.
    Napoli, D. R.
    Wadsworth, R.
    Ghugre, S. S.
    Raut, R.
    Al-Azri, H.
    Algora, A.
    de Angelis, G.
    Atac, A.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    Boso, A.
    Clement, E.
    Debenham, D. M.
    Dombradi, Zs.
    Erturk, S.
    Gadea, A.
    Ghazi Moradi, Farnaz
    Gottardo, A.
    Huyuk, T.
    Ideguchi, E.
    Li, H.
    Michelagnoli, C.
    Modamio, V.
    Nyberg, J.
    Palacz, M.
    Petrache, C. M.
    Recchia, F.
    Sandzelius, M.
    Siciliano, M.
    Timar, J.
    Valiente-Dobon, J. J.
    Xiao, Z. G.
    M1 and E2 transition rates from core-excited states in semi-magic 94RuManuscript (preprint) (Other academic)
    Abstract [en]

    Lifetimes of high-spin states have been measured in the semi-magic (N=50) nucleus 94Ru. Excited states in 94Ru were populated in the 58Ni(40Ca, 4p)94Ru fusion-evaporation reaction at the Grand Accelerateur National d’Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from γ-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm2 metallic 58Ni target. In total eight excited-state lifetimes in the angular momentum range I = (13 − 20)ħ have been measured, five of which were determined for the first time. The deduced corresponding B(M1) and B(E2)reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

  • 16.
    Ghazi Moradi, Farnaz
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Sandzelius, Mikael
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Atac, Ayse
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Hadinia, Baharak
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Andgren, Karin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Khaplanov, Anton
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Eeckhaudt, S.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Grahn, T.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Greenlees, P. T.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Jones, P. M.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Julin, R.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Juutinen, S.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Ketelhut, S.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Leino, M.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Nyman, M.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Rahkila, P.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Sarén, J.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Scholey, C.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Sorri, J.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Uusitalo, J.
    Department of Physics, University of Jyväskylä, Jyväskylä, Finland.
    Ganioglu, E.
    Science Faculty, Physics Department, Istanbul University, Istanbul, Turkey.
    Thomson, J.
    Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK.
    Joss, D. T.
    Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK.
    Page, R. D.
    Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK.
    Ertürk, S.
    CCLRC Daresbury Laboratory, Daresbury, Warrington, UK.
    Simpson, J.
    CCLRC Daresbury Laboratory, Daresbury, Warrington, UK.
    Gomez Hornillos, M. B.
    Seccio d'Enginyeria Nuclear, Universitat Politecnica de Catalunya, Barcelona, Spain.
    Bianco, L.
    Department of Physics, University of Guelph, Ontario, Canada.
    High-spin study of 162Ta2011In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 84, no 6, p. 064312-Article in journal (Refereed)
    Abstract [en]

    Excited states in the odd-odd neutron deficient nucleus (162)Ta (Z = 73, N = 89) have been studied for the first time. The gamma spectroscopy analysis using gamma - gamma - gamma coincidences revealed a strongly coupled rotational structure that was established up to large angular momentum states. The rotational band was assigned to the configuration pi h(11/2)[514]9/2 circle times nu i(13/2)[660]1/2 based on its rotational and electromagnetic properties. The data are interpreted within the framework of total Routhian surface calculations, which suggests an axially symmetric shape with a gamma-softminimum at beta(2) approximate to 0.16 and gamma approximate to 6 degrees. The crossing of the signature partners observed in heavier (N >= 91) odd-odd nuclides in this mass region is found to be absent at N = 89. This might be correlated with a change in S-band structure above the paired band crossing at these neutron numbers.

  • 17.
    Ghazi Moradi, Farnaz
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ataç, Ayşe
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Doncel, Maria
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    et al.,
    Spectroscopy of the neutron deficient N=50 nucleus 95Rh2014Manuscript (preprint) (Other academic)
  • 18.
    Ghazi Moradi, Farnaz
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ataç, Ayşe
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Doncel, Maria
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    de France, G.
    Clement, E.
    Nyberg, J.
    Gengelbach, A.
    Nyako, B. M.
    Gal, J.
    Kalinka, G.
    Molnar, J.
    Timar, J.
    Sohler, D.
    Dombradi, Zs.
    Kuti, I.
    Juhasz, K.
    Napoli, D. R.
    Gottardo, A.
    Modamio, V.
    Wadsworth, R.
    Henry, T. W.
    Nichols, A. J.
    Al-Azri, H.
    Palacz, M.
    Ideguchi, E.
    Aktas, O.
    Di Nitto, A.
    Dijon, A.
    Hueyuek, T.
    Jaworski, G.
    John, P. R.
    Yilmaz, B.
    Spectroscopy of the neutron-deficient N=50 nucleus Rh-952014In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 89, no 4, p. 044310-Article in journal (Refereed)
    Abstract [en]

    The neutron-deficient semimagic (neutron number N = 50) Rh-95 nucleus has been produced at high spins using the projectile-target system Ca-40 + Ni-58 at 125 MeV beam energy. The gamma-decays of levels populated by the 3p fusion evaporation reaction channel were studied using gamma-gamma coincidences, and 20 new gamma-ray transitions involving 15 new positive-and negative-parity states were observed. Spin and parity for many of the excited states were firmly deduced for the first time using the combined directional angular correlation and direction-polarization techniques. The observed structures are discussed within the framework of large-scale shell model calculations. E1 transition strengths were deduced and used together with the results of the shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

  • 19.
    Ghazi Moradi, Farnaz
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ataç, Ayşe
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Doncel, Maria
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    et al.,
    Character of particle-hole excitations in Ru-94 deduced from gamma-ray angular correlation and linear polarization measurements2014In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 89, no 1, p. 0143011-0143019Article in journal (Refereed)
    Abstract [en]

    Linear polarization and angular correlations of γ-rays depopulating excited states in the neutron-deficient nucleus 9444Ru50 have been measured, enabling firm spin-parity assignments for several excited states in this nucleus. The deduced multipolarities of strong transitions in the yrast structure were found to be mostly of stretched M1, E1, and E2 types and, in most cases, in agreement with previous tentative assignments. The deduced multipolarity of the 1869 keV and the connecting 257 and 1641 keV transitions indicates that the state at 6358 keV excitation energy has spin parity 12−1 rather than 12+3 as proposed in previous works. The presence of a 12−1 state is interpreted within the framework of large-scale shell-model calculations as a pure proton-hole state dominated by the π(p−11/2⊗g−59/2) and π(p−13/2⊗g−59/2) configurations. A new positive-parity state is observed at 6103 keV and is tentatively assigned as 12+2. The 14−1 state proposed earlier is reassigned as 13−4 and is interpreted as being dominated by neutron particle-hole core excitations. The strengths of several E1 transitions have been measured and are found to provide a signature of core-excited configurations.

  • 20.
    Hadinia, B.
    et al.
    Univ Guelph, Dept Phys, Guelph, ON, Canada..
    Garrett, P. E.
    Univ Guelph, Dept Phys, Guelph, ON, Canada..
    Svensson, C. E.
    Univ Guelph, Dept Phys, Guelph, ON, Canada..
    Carroll, R. J.
    Univ Liverpool, Dept Phys, Oliver Lodge Lab, Liverpool, Merseyside, England..
    Page, R. D.
    Univ Liverpool, Dept Phys, Oliver Lodge Lab, Liverpool, Merseyside, England..
    Joss, D. T.
    Univ Liverpool, Dept Phys, Oliver Lodge Lab, Liverpool, Merseyside, England..
    Darby, I. G.
    Univ Liverpool, Dept Phys, Oliver Lodge Lab, Liverpool, Merseyside, England..
    Paul, E. S.
    Univ Liverpool, Dept Phys, Oliver Lodge Lab, Liverpool, Merseyside, England..
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Back, Tove
    KTH, School of Engineering Sciences (SCI), Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Johnson, A.
    KTH, School of Engineering Sciences (SCI), Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Grahn, T.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Greenlees, P. T.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Jones, P. M.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Julin, R.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Ketelhut, S.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Leino, M.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Rahkila, P.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Sandzelius, M.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Scholey, C.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    Uusitalo, J.
    Univ Jyvaskyla, Dept Phys, Jyvaskyla, Finland..
    IN-BEAM gamma-RAY SPECTROSCOPY ABOVE THE HIGH-SPIN ISOMERIC STATE IN Lu-1552013In: CAPTURE GAMMA-RAY SPECTROSCOPY AND RELATED TOPICS / [ed] Garrett, PE Hadinia, B, WORLD SCIENTIFIC PUBL CO PTE LTD , 2013, p. 139-144Conference paper (Refereed)
    Abstract [en]

    Excited states in Lu-155 have been studied at the Accelerator Laboratory of the University of Jyvaskyla in Finland. The Lu-155 nuclei were populated using the reaction of Ni-58 on (102)pd at a beam energy of 280 MeV. The nuclei of interest were selected using the RITU gas filled recoil separator and the prompt gamma rays belonging to 155Lu were identified using the recoil-decay tagging technique. The gamma-ray transitions de-exciting the excited states above the high-spin isomeric a-decaying state in Lu-155 have been identified. A gamma-ray coincidence analysis shows that the previously reported level scheme for Lu-155 should be revised.

  • 21. Huang, Y.
    et al.
    Xiao, Z. G.
    Zhu, S. J.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Xu, Q.
    Cheng, W. J.
    Li, H. J.
    Lyu, L. M.
    Wang, R. S.
    Yan, W. H.
    Yi, H.
    Zhang, Y.
    Chen, Q. M.
    He, C. Y.
    Hu, S. P.
    Li, C. B.
    Li, H. W.
    Luo, P. W.
    Wu, X. G.
    Wu, Y. H.
    Zheng, Y.
    Zhong, J.
    High-spin structures in the Xe-129 nucleus2016In: Physical Review C, ISSN 2469-9985, Vol. 93, no 6, article id 064315Article in journal (Refereed)
    Abstract [en]

    High-spin states in the Xe-129 nucleus are studied with the reaction Sn-124(Be-9,4n) at a beam energy of 36 MeV. The level scheme is extended significantly. For the positive-parity band, the alpha = +1/2 and the alpha = -1/2 signature components are combined to form a complete band structure based on the 3/2(+) state with spin and parity up to 21/2(+). For the negative-parity band based on the 11/2(-) state, the alpha = +1/2 signature component is newly established and both the alpha = +1/2 and the alpha = -1/2 signature components also form a complete band structure up to the 35/2(-) state. The positive-and negative-parity bands are proposed to originate from nu d(3/2) 3/2(+)[402] and nu h(11/2)11/2(-)[505] Nilsson configurations, respectively. A backbending is observed in the negative-parity band, which originates from the alignments of two h(11/2) protons according to crank shell model calculations. Based on the total Routhian surface and quasiparticle triaxial rotor model calculations, the negative-parity band is interpreted as a triaxially deformed shape with gamma approximate to -30 degrees, while the positive-parity band is associated with. softness, in accordance with previous studies. In the high-spin states, three decoupled bands and one oblate band with gamma approximate to -60 degrees are newly identified. The systematics and other characteristics of these bands are discussed.

  • 22. Jia, L. Y.
    et al.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Generalized-seniority pattern and thermal properties in even Sn isotopes2016In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 94, no 4, article id 044312Article in journal (Refereed)
    Abstract [en]

    Even tin isotopes of mass number A = 108-124 are calculated with realistic interactions in the generalized-seniority approximation of the nuclear shell model. For each nucleus, we compute the lowest 10 000 states (5000 of each parity) up to around 8 MeV in excitation energy, by allowing as many as four broken pairs. The lowest 50 eigen energies of each parity are compared with the exact results of the large-scale shell-model calculation. The wave functions of the midshell nuclei show a clear pattern of the stepwise breakup of condensed coherent pairs with increasing excitation energy. We also compute in the canonical ensemble the thermal properties-level density, entropy, and specific heat-in relation to the thermal pairing phase transition.

  • 23.
    Jiang, Hui
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lei, Y.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Zhao, Y. M.
    Magnetic moments of low-lying states in tin isotopes within the nucleon-pair approximation2014In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 89, no 1, p. 014320-Article in journal (Refereed)
    Abstract [en]

    The magnetic moments of the first excited 2(+) state in even-even nuclei Sn102-130 and the low-lying yrast states in odd-mass nuclei Sn-101-109,Sn-123-131 are calculated within the framework of the nucleon-pair approximation (NPA) of the shell model, by using the standard multipole-multipole interaction. Our calculations agree reasonably well with available experimental data. The g(2(1)(+)) values, as well as the contributions from their spin and orbital angular momentum components, are evaluated in terms of the small NPA subspace spanned by S and D nucleon pairs. The magnetic moment is suggested to be a sensitive probe of the nuclear wave function in this region.

  • 24.
    Jiang, Hui
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Lei, Y.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Zhao, Y. M.
    Nucleon pair approximation description of the low-lying structure of Te-108,Te-109 and I-1092013In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 88, no 4, p. 044332-Article in journal (Refereed)
    Abstract [en]

    The low-lying level schemes and electromagnetic transitions of Te-109, I-109, and the neighboring even-even nucleus Te-108 are calculated within the framework of the SD-pair approximation of the nuclear shell model. Good agreement is obtained between the calculated results and experimental data. The favored components of low-lying bands are discussed in the collective nucleon-pair subspace. The weak-coupling picture shown in these nuclei and its relationship with residual quadrupole-quadrupole interaction between valence protons and neutrons are analyzed.

  • 25. Jiao, L. F.
    et al.
    Sun, Z. H.
    Xu, Z. X.
    Xu, F. R.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Correlated-basis method for shell-model calculations2014In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 90, no 2, p. 024306-Article in journal (Refereed)
    Abstract [en]

    We present a basis selection method for truncated shell-model calculations. In this method, the correlated basis is constructed with the eigenvectors of the Hamiltonian that is diagonalized in each partition of the shell model. A truncation scheme is established by naturally taking the low-lying correlated-basis vectors in different partitions, which is equivalent to the jj-coupling scheme of the shell model when all the correlated-basis vectors are considered. The results are compared with standard shell-model calculations. The convergence properties of the correlated-basis method are discussed.

  • 26.
    Li, Hongjie
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics. Tsinghua University, People's Republic of China.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Doncel, Maria
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Jakobsson, Ulrika
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics. University of Jyvaskyla, Finland.
    Auranen, K.
    Boenig, S.
    Drummond, M. C.
    Grahn, T.
    Greenlees, P.
    Herzan, A.
    Julin, R.
    Juutinen, S.
    Konki, J.
    Kroell, T.
    Leino, M.
    McPeake, C.
    O'Donnell, D.
    Page, R. D.
    Pakarinen, J.
    Partanen, J.
    Peura, P.
    Rahkila, P.
    Ruotsalainen, P.
    Sandzelius, M.
    Saren, J.
    Saygi, B.
    Scholey, C.
    Sorri, J.
    Stolze, S.
    Taylor, M. J.
    Thornthwaite, A.
    Uusitalo, J.
    Xiao, Z. G.
    Recoil-decay tagging spectroscopy of W-162(74)882015In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 92, no 1, article id 014326Article in journal (Refereed)
    Abstract [en]

    Excited states in the highly neutron-deficient nucleus W-162 have been investigated via the Mo-92(Kr-78, 2 alpha) W-162 reaction. Prompt gamma rays were detected by the JUROGAM II high-purity germanium detector array and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and identified with the gamma recoil electron alpha tagging (GREAT) spectrometer at the focal plane of RITU. gamma rays from W-162 were identified uniquely using mother-daughter and mother-daughter-granddaughter alpha-decay correlations. The observation of a rotational-like ground-state band is interpreted within the framework of total Routhian surface (TRS) calculations, which suggest an axially symmetric ground-state shape with a gamma-soft minimum at beta(2) approximate to 0.15. Quasiparticle alignment effects are discussed based on cranked shell model calculations. New measurements of the W-162 ground-state alpha-decay energy and half-life were also performed. The observed alpha-decay energy agrees with previous measurements. The half-life of W-162 was determined to be t(1/2) = 990(30) ms. This value deviates significantly from the currently adopted value of t(1/2) = 1360(70) ms. In addition, the alpha-decay energy and half-life of Os-166 were measured and found to agree with the adopted values.

  • 27.
    Li, Hongjie J.
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Xiao, Z. G.
    Zhu, S. J.
    Patial, Monika
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics.
    Zhang, Z.
    Wang, R. S.
    Yi, H.
    Yan, W. H.
    Cheng, W. J.
    Huang, Y.
    Lyu, L. M.
    Zhang, Y.
    Wu, X. G.
    He, C. Y.
    Zheng, Y.
    Li, G. S.
    Li, C. B.
    Li, H. W.
    Liu, J. J.
    Luo, P. W.
    Hu, S. P.
    Wang, J. L.
    Wu, Y. H.
    Collective band structures in the Tc-99 nucleus2015In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 91, no 5, article id 054314Article in journal (Refereed)
    Abstract [en]

    Excited states in Tc-99 with energies up to 6 MeV have been populated using the Zr-96(Li-7, 4n)Tc-99 reaction with a laboratory beam energy of 35 MeV. Coincident gamma rays from excited nuclei produced in the reactions were detected using an array of coaxial, planar, and clover-type high-purity germanium detectors. A total of 60 new gamma-ray transitions and 21 new levels are identified and placed into a new level scheme. Two collective bands assigned to be built on the pi g(9/2)[422]5/2(+) and pi p(1/2)[301]1/2(-) Nilsson configurations have been extended with spins up to 35/2 and 33/2 h, respectively. Backbending and signature inversion have been observed in the yrast band. The large signature splitting of the positive-parity band in Tc-99 may be caused by a triaxial deformation, which agrees well with the electromagnetic properties, theoretical calculations based on total Routhian surface, and triaxial particle-rotor model calculations.

  • 28.
    Li, Hongjie
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Xiao, Z. G.
    Zhu, S. J.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Yeoh, E. Y.
    Zhang, Z.
    Wang, R. S.
    Yi, H.
    Yan, W. H.
    Xu, Q.
    Wu, X. G.
    He, C. Y.
    Zheng, Y.
    Li, G. S.
    Li, C. B.
    Li, H. W.
    Liu, J. J.
    Hu, S. P.
    Wang, J. L.
    Yao, S. H.
    Reinvestigation of the collective band structures in odd-odd Pm-138 nucleus2015In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 51, no 5, article id 60Article in journal (Refereed)
    Abstract [en]

    The high-spin states in the odd-odd Pm-138 nucleus have been reinvestigated via the Te-124(F-19, 5n) reaction at the beam energy of 103MeV. Most of the known transitions and levels are confirmed. A number of bands are revised and one new band has been established. For the yrast pi h(11/2) circle times nu h(11/2) band based on 8(+) state, no evidence supporting the occurence of signature inversion is found. The experimental and theoretical B(M1)/B(E2) ratios have been calculated for band (2), which support the pi g(7/2)[413]5/2(+) circle times nu h(11/2)[514]9/2(-) Nilsson configuration assignment. Four bands with Delta I = 2 transitions are tentatively assigned as doubly decoupled bands. The other three bands are proposed as oblate-triaxial bands. The possible configuration assignments for these bands are also discussed under the calculations of total Routhian surface and particle-rotor model.

  • 29. Li, K. A.
    et al.
    Lam, Y. H.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Tang, X. D.
    Zhang, N. T.
    beta-decay rate of Fe-59 in shell burning environment and its influence on the production of Fe-60 in a massive star2016In: Physical Review C - Nuclear Physics, ISSN 2469-9985, Vol. 94, no 6, article id 065807Article in journal (Refereed)
    Abstract [en]

    We deduced the stellar beta-decay rate of Fe-59 at typical carbon-shell burning temperature by taking the experimental Gamow-Teller transition strengths of the Fe-59 excited states. The result is also compared with those derived from large-scale shell model calculations. The new rate is up to a factor of 2.5 lower than the theoretical rate of Fuller, Fowler, and Newman (FFN) and up to a factor of 5 higher than decay rate of Langanke and Martinez-Pinedo (LMP) in the temperature region 0.5 <= T <= 2 GK. We estimated the impact of the newly determined rate on the synthesis of cosmic gamma emitter Fe-60 in C-shell burning and explosive C/Ne burning using a one-zone model calculation. Our results show that Fe-59 stellar beta decay plays an important role in Fe-60 nucleosynthesis, even though the uncertainty of the decay rate is rather large due to the error of B(GT) strengths.

  • 30. Li, K.
    et al.
    Lam, Y. H.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Tang, X.
    Zhang, N.
    The beta-decay rates of Fe-59 isotopes in shell burning environments and their influences on the production of Fe-60 in massive star2016In: 13TH INTERNATIONAL SYMPOSIUM ON ORIGIN OF MATTER AND EVOLUTION OF GALAXIES (OMEG2015), EDP Sciences, 2016, article id 04006Conference paper (Refereed)
    Abstract [en]

    The experimental B(GT) strengths of the Fe-59 excited states were employed to determine the transition strengths which greatly contribute Fe-59 stellar beta-decay at typical carbon shell burning temperature. The result has been compared with the theoretical rates FFN (Fuller-Fowler-Newman) and LMP (Langanke&Martinez-Pinedo). Impact of the newly determined rate on the synthesis of cosmic gamma-emitter 60Fe has also been studied using one-zone model calculation. Our results show Fe-59 stellar beta-decay rate plays an important role in the Fe-60 nucleosynthesis. However the uncertainty of the decay rate is rather large due to the error of B(GT) strength that requires further studies.

  • 31. Procter, M. G.
    et al.
    Cullen, D. M.
    Scholey, C.
    Ruotsalainen, P.
    Angus, L.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Dewald, A.
    Fransen, C.
    Grahn, T.
    Greenlees, P. T.
    Hackstein, M.
    Jakobsson, U.
    Jones, P. M.
    Julin, R.
    Juutinen, S.
    Ketelhut, S.
    Leino, M.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Lumley, N. M.
    Mason, P. J. R.
    Nieminen, P.
    Nyman, M.
    Pakarinen, J.
    Pissulla, T.
    Peura, P.
    Rahkila, P.
    Revill, J.
    Rigby, S. V.
    Rother, W.
    Sandzelius, M.
    Saren, J.
    Sorri, J.
    Taylor, M. J.
    Uusitalo, J.
    Wady, P.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Xu, F. R.
    Anomalous transition strength in the proton-unbound nucleus (109)(53)I562011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 704, no 3, p. 118-122Article in journal (Refereed)
    Abstract [en]

    A lifetime measurement has been made for the first excited 11/2(+) state in the proton-unbound nucleus (109)(53)I56 using the recoil-distance Doppler-shift method in conjunction with recoil-proton tagging. The experimental reduced transition probability is considerably smaller than the prediction of theoretical shell-model calculations using the CD-Bonn nucleon-nucleon potential. The discrepancy between the theoretical and experimental reduced transition strengths in this work most likely arises from the inability of the current shell-model calculations to accurately account for the behavior of the unbound nuclear states.

  • 32. Procter, M. G.
    et al.
    Cullen, D. M.
    Taylor, M. J.
    Pakarinen, J.
    Auranen, K.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Braunroth, T.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Dewald, A.
    Grahn, T.
    Greenlees, P. T.
    Jakobsson, U.
    Julin, R.
    Juutinen, S.
    Herzan, A.
    Konki, J.
    Leino, M.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Partanen, J.
    Peura, P.
    Rahkila, P.
    Ruotsalainen, P.
    Sandelius, M.
    Saren, J.
    Scholey, C.
    Sorri, J.
    Stolze, S.
    Uusitalo, J.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Isomer-tagged differential-plunger measurements in Xe-113(54)2013In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 87, no 1, p. 014308-Article in journal (Refereed)
    Abstract [en]

    The 278-keV M2 gamma decay from the vh(11/2) isomeric state in Xe-113 has been observed for the first time using the recoil-isomer tagging technique. The half-life of the isomer has been measured to be 6.9(3) mu s. The derived B(M2) value is in agreement with the trend of systematic measurements of M2 transition strengths in neutron-deficient tellurium and tin isotopes. The lifetime of the first excited state in the vh(11/2) band has been measured using the recoil distance Doppler-shift method. The extracted B(E2) value has been compared to theoretical CD-Bonn calculations and recent lifetime measurements in Te-109. This comparison of B(E2) values has been used to shed light on the possible influence of collective degrees of freedom on M2 transition strengths in the most neutron-deficient xenon nuclei. The vh(11/2) band is deduced to have a degree of deformation comparable with the ground-state bands of the even-mass xenon isotopes. However, the value deduced in this work indicates a loss of collective behavior when compared with the lower-mass Te-109. This result suggests that, while changes in deformation may be partly responsible for the observed trend in B(M2) values for increasing Z, other effects may also be present.

  • 33.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Alpha decay as a probe for the structure of neutron-deficient nuclei2016In: Reviews in Physics, ISSN 2405-4283, Vol. 1, p. 77-89Article in journal (Refereed)
    Abstract [en]

    The advent of radioactive ion beam facilities and new detector technologies have opened up new possibilities to investigate the radioactive decays of highly unstable nuclei, in particular the proton emission, α decay and heavy cluster decays from neutron-deficient (or proton-rich) nuclei around the proton drip line. It turns out that these decay measurements can serve as a unique probe for studying the structure of the nuclei involved. On the theoretical side, the development in nuclear many-body theories and supercomputing facilities have also made it possible to simulate the nuclear clusterization and decays from a microscopic and consistent perspective. In this article we would like to review the current status of these structure and decay studies in heavy nuclei, regarding both experimental and theoretical opportunities. We then discuss in detail the recent progress in our understanding of the nuclear α formation probabilities in heavy nuclei and their indication on the underlying nuclear structure.

  • 34.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    alpha FORMATION PROBABILITIES IN NUCLEI AND PAIRING COLLECTIVITY2010In: NUCLEAR STRUCTURE IN CHINA 2010 / [ed] Bai, HB Meng, J Zhao, EG Zhou, SG, WORLD SCIENTIFIC PUBL CO PTE LTD , 2010, p. 169-174Conference paper (Refereed)
    Abstract [en]

    alpha formation amplitudes extracted from experimental data are presented and an abrupt change around the N = 126 shell closure is noted. It is explained as a sudden hindrance of the clustering of nucleons. The clustering induced by the pairing mode acting upon the four nucleons is inhibited if the configuration space does not allow a proper manifestation of the pairing collectivity.

  • 35.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Differential evolution algorithm for global optimizations in nuclear physics2017In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 44, no 4, article id 045107Article in journal (Refereed)
    Abstract [en]

    We explore the applicability of the differential evolution algorithm in finding the global minima of three typical nuclear structure physics problems: the global deformation minimum in the nuclear potential energy surface, the optimization of mass model parameters and the lowest eigenvalue of a nuclear Hamiltonian. The algorithm works very effectively and efficiently in identifying the minima in all problems we have tested. We also show that the algorithm can be parallelized in a straightforward way.

  • 36.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Double binding energy differences: Mean-field or pairing effect?2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 717, no 4-5, p. 436-440Article in journal (Refereed)
    Abstract [en]

    In this Letter we present a systematic analysis on the average interaction between the last protons and neutrons in atomic nuclei, which can be extracted from the double differences of nuclear binding energies. The empirical average proton-neutron interaction V-pn thus derived from experimental data can be described in a very simple form as the interplay of the nuclear mean field and the pairing interaction. It is found that the smooth behavior as well as the local fluctuations of the V-pn in even-even nuclei with N not equal Z are dominated by the contribution from the proton-neutron monopole interactions. A strong additional contribution from the isoscalar monopole interaction and isovector proton-neutron pairing interaction is seen in the V-pn for even-even N = Z nuclei and for the adjacent odd-A nuclei with one neutron or proton being subtracted.

  • 37.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Energy expressions for n=3 and 4 systems in a single-j shell2010In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 81, no 3, p. 034318-Article in journal (Refereed)
    Abstract [en]

    For systems with three and four fermions within a single-j shell, analytical expressions for the state energies are presented from a decomposition of the angular momentum. In some important cases the expressions acquire a very simple form. The expression may help us in understanding the structure of isomeric states. The decomposition also makes it possible to construct the algebraic condition for conservation of seniority.

  • 38.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Large-scale configuration interaction description of the structure of nuclei around 100Sn and 208Pb2016In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 742, no 1, article id 012030Article in journal (Refereed)
    Abstract [en]

    In this contribution I would like to discuss briefly the recent developments of the nuclear configuration interaction shell model approach. As examples, we apply the model to calculate the structure and decay properties of low-lying states in neutron-deficient nuclei around 100Sn and 208Pb that are of great experimental and theoretical interests.

  • 39.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Partial conservation of seniority and its unexpected influence on E2 transitions in g(9/2) nuclei2017In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 773, p. 616-619Article in journal (Refereed)
    Abstract [en]

    There exist two uniquely defined v = 4 states in systems within a j = 9/2 subshell, which automatically conserve seniority and do not mix with other states. Here I show that the partial conservation of seniority plays an essential role in our understanding of the electric quadrupole transitions of the semimagic nuclei involving j = 9/2 subshells, including the long-lived 8(+) isomer in (94) Ru. The effects of configuration mixing from neighboring subshells on the structure of those unique states are analyzed. It is shown that a sharp transition from pure seniority coupling to a significant mixture between the v = 2 and v = 4 states may be induced by the cross-orbital non-diagonal interaction matrix elements. Such strong mixture is essential to explain the observed E2 transition properties of N = 50 isotones Pd-96 and Ru-94.

  • 40.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Partial conservation of seniority in the j=9/2 shell: Analytic and numerical studies2011In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 83, no 1, p. 014307-Article in journal (Refereed)
    Abstract [en]

    Recent studies show that for systems with four identical fermions in the j = 9/2 shell, two special states, which have seniority v = 4 and total spins I = 4 and 6, are eigenstates of any two-body interaction. These states have good seniority for an arbitrary interaction. In this work, an analytic proof is given to this peculiar occurrence of partial conservation of seniority, which is the consequence of the special property of certain coefficients of fractional parentage. Further calculations did not reveal its existence in systems with other n and/or I for shells with j <= 15/2.

  • 41.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Seniority and truncation schemes for the nuclear configuration interaction approach2015In: Romanian Journal of Physics, ISSN 1221-146X, Vol. 60, no 5-6, p. 782-791Article in journal (Refereed)
    Abstract [en]

    In this contribution I would like to review a few issues on the recent developments concerning the truncation schemes for the nuclear configuration interaction shell model approach. The seniority scheme is a way to solve the pairing Hamiltonian exactly and a good starting point for shell model calculations. Physically meaningful states may also be selected based on importance truncations from a perturbation perspective.

  • 42.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics.
    Shell-model configuration-interaction description of quadrupole collectivity in Te isotopes2016In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 94, no 3, article id 034310Article in journal (Refereed)
    Abstract [en]

    Systematic calculations on the spectroscopy and transition properties of even-even Te isotopes are carried out by using the large-scale shell-model configuration-interaction approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally spaced pattern whereas the few known E2 transitions show rotational-like behavior. This cannot be explained by available collective models. My calculations reproduce well the equally spaced spectra of those isotopes as well as the constant behavior for the B(E2) values of Te-114. The calculated B(E2) values of neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The B(E2) of light isotopes can exhibit a nearly constant behavior up to high spins. It is shown that this is related to the enhanced neutron-proton correlation when approaching N = 50.

  • 43.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Spin-Aligned Neutron-Proton Pair Coupling Scheme2012In: Progress of Theoretical Physics Supplement, ISSN 0375-9687, no 196, p. 414-420Article in journal (Refereed)
    Abstract [en]

    The recently proposed spin-aligned neutron-proton pair coupling scheme is studied within a non-orthogonal basis in term of the multistep shell model. This also allows us to identify simultaneously the roles played by different configurations such as the normal pairing term.

  • 44.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    THE ANOMALOUS 14C-DATING β DECAY PROBLEM REEXAMINED: INDICATION ON THE MONOPOLE DEFICIENCY OF REALISTIC NN INTERACTIONS2012In: Romanian Journal of Physics, ISSN 1221-146XArticle in journal (Refereed)
  • 45.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    The structure of tin isotopes with a global optimized effective interaction2013In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 413, no 1, p. 012037-Article in journal (Refereed)
    Abstract [en]

    A systematic shell model calculation on the structure of light tin isotopes is presented with a monopole-optimized effective interaction. We started with the realistic CD-Bonn potential. The unknown single-particle energies and the T = 1 monopole interactions are determined by fitting to the binding energies of the yrast states of nuclei Sn102-132. The mean deviation from experimental data is around 120 keV. In particular, we analyzed the origin of the spin inversion between Sn-101 and Sn-103.

  • 46.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Theoretical uncertainties of the Duflo-Zuker shell-model mass formulae2015In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 42, no 4, article id 045104Article in journal (Refereed)
    Abstract [en]

    It is becoming increasingly important to understand the uncertainties of nuclear mass model calculations and their limitations when extrapolating to driplines. In this paper we evaluate the parameter uncertainties of the Duflo-Zuker (DZ) shell model mass formulae by fitting to the latest experimental mass compilation AME2012 using the least square and minimax fitting procedures. We also analyze the propagation of the uncertainties in binding energy calculations when extrapolated to driplines. The parameter uncertainties and uncertain propagations are evaluated with the help of the covariance matrix thus derived. Large deviations from the extrapolations of AME2012 are seen in superheavy nuclei. A simplified version of the DZ model (DZ19) with much smaller uncertainties than that of DZ33 is proposed. Calculations are compared with results from other mass formulae. Systematics on the uncertainty propagation as well as the positions of the driplines are also presented. The DZ mass formulae are shown to be well defined with good extrapolation properties and rather small uncertainties, even though some of the parameters of the full DZ33 model cannot be fully determined by fitting to available experimental data.

  • 47.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Andreyev, A.
    University of the West of Scotland.
    Huyse, M.
    K.U. Leuven.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Van Duppen, P.
    K.U. Leuven.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Suppression of alpha formation probability around the N = 126 shell closure2011In: Frontiers In Nuclear Structure, Astrophysics, And Reactions (FINUSTAR 3), 2011, Vol. 1377, p. 296-300Conference paper (Refereed)
    Abstract [en]

    alpha formation amplitudes extracted from experimental data are presented and an abrupt change around the N = 126 shell closure is noted. It is explained as a sudden hindrance of the clustering of nucleons. The clustering induced by the pairing mode acting upon the four nucleons is inhibited if the configuration space does not allow a proper manifestation of the pairing collectivity.

  • 48.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Andreyev, A. N.
    Huyse, M.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Van Duppend, P.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    On the validity of the Geiger-Nuttall alpha-decay law and its microscopic basis2014In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 734, p. 203-206Article in journal (Refereed)
    Abstract [en]

    The Geiger-Nuttall (GN) law relates the partial alpha-decay half-life with the energy of the escaping alpha particle and contains for every isotopic chain two experimentally determined coefficients. The expression is supported by several phenomenological approaches, however its coefficients lack a fully microscopic basis. In this paper we will show that: (1) the empirical coefficients that appear in the GN law have a deep physical meaning, and (2) the GN law is successful within the restricted experimental data sets available so far, but is not valid in general. We will show that, when the dependence of logarithm values of the alpha formation probability on the neutron number is not linear or constant, the GN law is broken. For the alpha decay of neutron-deficient nucleus Po-186, the difference between the experimental half-life and that predicted by the GN law is as large as one order of magnitude.

  • 49.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Andreyev, A. N.
    Huyse, M.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Van Duppen, P.
    Wyss, Ramon A.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Abrupt changes in alpha-decay systematics as a manifestation of collective nuclear modes2010In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 81, no 6, p. 064319-Article in journal (Refereed)
    Abstract [en]

    An abrupt change in alpha-decay systematics around the N = 126 neutron shell closure is discussed. It is explained as a sudden hindrance of the clustering of the nucleons that eventually form the a particle. This is because the clustering induced by the pairing mode acting upon the four nucleons is inhibited if the configuration space does not allow a proper manifestation of the pairing collectivity.

  • 50.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Blomqvist, Jan
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Bäck, Torbjörn
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Coherence features of the spin-aligned neutron-proton pair coupling scheme2012In: Physica scripta. T, ISSN 0281-1847, Vol. T150, p. 014031-Article in journal (Refereed)
    Abstract [en]

    The seniority scheme has been shown to be extremely useful for the classification of nuclear states in semi-magic nuclei. The neutron-proton (np) correlation breaks the seniority symmetry in a major way. As a result, the corresponding wave function is a mixture of many components with different seniority quantum numbers. In this paper, we show that the np interaction may favor a new kind of coupling in N = Z nuclei, i.e. the so-called isoscalar spin-aligned np pair mode. Shell model calculations reveal that the ground and low-lying yrast states of the N = Z nuclei Pd-92 and Cd-96 may be mainly built upon such spin-aligned np pairs, each carrying the maximum angular momentum J = 9 allowed by the shell 0 g(9/2) which is dominant in this nuclear region.

12 1 - 50 of 97
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