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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.
    Betan, Rodolfo Id
    et al.
    KTH, Superseded Departments, Physics.
    Liotta, Roberto J.
    KTH, Superseded Departments, Physics.
    Sandulescu, Nicolae
    Vertse, Tamas
    KTH, Superseded Departments, Physics.
    A shell model representation with antibound states2004In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 584, no 1-2, p. 48-57Article in journal (Refereed)
    Abstract [en]

    An unified shell model scheme is introduced that evaluates simultaneously the contributions of bound single-particle states, Gamow resonances and antibound states to processes occurring in the continuum part of nuclear spectra. This new scheme allows us to study the effect of the antibound pole and the remaining part of the complex continuum separately. The calculations, performed in the complex energy plane, are applied to the study of weakly bound nuclei. The influence of antibound states upon physical quantities in light as well as in heavy nuclei is assessed.

  • 3.
    Betan, Rodolfo Id.
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics.
    Sandulescu, Neculai
    KTH, School of Engineering Sciences (SCI), Physics.
    Vertse, Tamas
    KTH, School of Engineering Sciences (SCI), Physics.
    Description of the continuum part of the spectrum by using the complex. energy plane2005In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 31, no 8, p. S1329-S1336Article in journal (Refereed)
    Abstract [en]

    Processes occurring in the continuum part of the spectrum are described by using a basis consisting of bound and antibound states plus Gamow resonances and the continuum background. The calculations, performed in the complex energy plane, are applied to the study of weakly bound nuclei. The influence of antibound states upon physical quantities in halo nuclei is assessed.

  • 4.
    Bhagwat, Ameeya
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics. UM-DAE Centre for Excellence in Basic Sciences, India.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cluster decay in the superallowed alpha decay region2017In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 3, article id 031302Article in journal (Refereed)
    Abstract [en]

    The emissions of a particles and protons are the dominant decay channels in the neutron-deficient nuclei corresponding to the sdg major shell. The possibility of cluster emission is explored here. It is shown that the cluster decay mode has a small yet sizable branching ratio.

  • 5.
    Bhagwat, Ameeya
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics. UM-DAE Centre for Excellence in Basic Sciences, Mumbai, India.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Consistent description of the cluster-decay phenomenon in transactinide nuclei2015In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 92, no 4Article in journal (Refereed)
    Abstract [en]

    Systematic investigation of the known even-even transactinide cluster emitters has been carried out by considering the cluster as a point particle and using the exact quantum mechanical treatment of the decay process. It is shown that the cluster decay phenomenon can be described reasonably well using a simple Woods-Saxon mean field. Sensitivity of the half-lives on various aspects of the mean field has been investigated in detail.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9.
    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.

  • 10. Civitarese, O.
    et al.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Mosquera, M. E.
    Effects of resonant and continuum states on the neutrino-nucleus cross section2008In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 78, no 6, p. 064308-Article in journal (Refereed)
    Abstract [en]

    Estimates of the neutrino-nucleus cross section, for the charged-current process nu + Pb-208 -> e(-) + Bi-208*, are presented. The nuclear structure calculations were performed by considering bound, resonant, and continuum states in the single-particle basis used to construct correlated proton-particle neutron-hole configurations. The observed features of the spectrum of Bi-208 were reproduced, as accurately as possible, by diagonalizing a phenomenological multipole-multipole interaction. Calculations of the cross section, for values of q <= 200 MeV, were performed, and the dependence of the results on the choice of the residual proton-neutron interaction was investigated. It is found that the inclusion of resonant states in the calculation of the nuclear wave functions increases the neutrino-nucleus cross section and that the contribution of the continuum is negligible.

  • 11. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics.
    Probing nuclear mean field by proton emission2007In: Romanian Reports in Physics, ISSN 1221-1451, E-ISSN 1841-8759, Vol. 59, no 2, p. 411-417Article in journal (Refereed)
    Abstract [en]

    We show that proton emission is a valuable tool to investigate mean field properties of exotic proton rich nuclei. We give a formula that relates the logarithm of the half-life, corrected by the centrifugal barrier, with the Somerfeld parameter in proton decay processes. The corresponding experimental data lie on two straigth lines which appear as a result of a sudden change in the nuclear shape, marking two regions of deformation. This feature provides a powerfull tool to assign experimentally quantum numbers and deformations in proton emitters.

  • 12. Delion, D. S.
    et al.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics. Alba Nova University Center, Sweden.
    Wyss, Ramon
    KTH. Alba Nova University Center, Sweden.
    Exact estimate of the alpha-decay rate and semiclassical approach in deformed nuclei2015In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 92, no 5, article id 051301Article in journal (Refereed)
    Abstract [en]

    We compare the quantum mechanical procedures to estimate the total alpha-decay width from deformed nuclei in the laboratory and intrinsic systems of coordinates. Our analysis shows that the total half-life estimated in the intrinsic frame by neglecting the rotational motion of the core (adiabatic approach) is one order of magnitude smaller at beta(2) = 0.3 than the corresponding value in the spherical case. A similar calculation in the laboratory system of coordinates by considering the core motion (giving the correct theoretical estimate) predicts a reduction by only a factor of 2. The widely used "angular WKB" (Wentzel-Kramers-Brillouin) semiclassical procedure provides decay widths which are comparable to the adiabatic approach. We propose a new and very simple semiclassical "angular momentum WKB" procedure to evaluate the decay width in deformed nuclei. It provides decay widths very close to the ones obtained by the exact laboratory coupling channels procedure.

  • 13. Delion, D. S.
    et al.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Simple approach to two-proton emission2013In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 87, no 3, p. 034328-Article in journal (Refereed)
    Abstract [en]

    The two-proton decay process is studied by using a simple approach within the framework of scattering theory. We assume that the decaying nucleus is in a pairing state and, therefore, the two-particle wave function on the nuclear surface corresponds to the two protons moving in time-reversed states. This allows us to sustain a simplified version of the decay where the protons are simultaneously emitted with the same energies. We thus obtain a coupled system of radial equations with outgoing boundary conditions. We use similar proton-proton interactions to solve BCS equations and to describe external two-proton dynamics. A strong dependence of the pairing gap and decay width upon the proton-proton interaction strength is revealed. The experimental half-lives of Fe-45 and Ni-48 are reproduced by using a realistic proton-proton interaction.

  • 14. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Schuck, P.
    Astier, A.
    Porquet, M. -G
    Shell model plus cluster description of negative parity states in Po-2122012In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 85, no 6, p. 064306-Article in journal (Refereed)
    Abstract [en]

    The intraband electromagnetic transitions in Po-210 and Pb-210 are well described within the shell model approach. In contrast, similar transitions in Po-212 are one order ofmagnitude smaller than the experimental values, suggesting the existence of an alpha-cluster component in the structure of this nucleus. To probe this assumption we introduced Gaussian-like components in the single-particle orbitals. We thus obtained an enhancement of intraband transitions, as well as a proper description of the absolute alpha-decay width in Po-212. We analyzed the recently measured unnatural parity states I- in Po-212 in terms of the collective octupole excitation in Pb-208 coupled to positive parity states in Pb-210. They are connected by relatively large dipole transitions to yrast positive natural parity states. We described E1 transitions by using the same alpha-cluster component and an effective neutron dipole charge e(nu) = -eZ/A. B(E2) values and absolute alpha-decay width in Po-212 are simultaneously described within the shell model plus a cluster component depending upon one free strength parameter.

  • 15. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    alpha decay of high-spin isomers in superheavy nuclei2007In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 76, no 4, p. 044301-Article in journal (Refereed)
    Abstract [en]

    Hindrance factors corresponding to alpha decay from two quasiparticle isomeric high K states are evaluated in superheavy nuclei. We found that the hindrance factors are very sensitive to the deformations and, therefore, they may constitute a powerful tool to extract spectroscopic information in these nuclei. The hindrance factors turn out to be very large, specially for nonaligned configurations. This indicates that if one of such states is reached the parent nucleus may become isomeric. It is also possible that alpha decay may not proceed through ground state to ground state chains but rather through excited states.

  • 16. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, Superseded Departments, Physics.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    High-spin proton emitters in odd-odd nuclei and shape changes2003In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 68, no 5, p. 054603-Article in journal (Refereed)
    Abstract [en]

    We present a formalism to describe proton emission from odd-odd nuclei based on a scatteringlike approach. Special emphasis is given to the case of transitions between states with different deformations. As an example we estimate the proton half-life of the odd-odd nucleus Cu-58 . Our calculations show that the change of deformation in the decay process has a significant influence on the half life. In addition, the angular momentum coupling of proton and neutron orbitals can result in an additional K hindrance of the decay. To fully account for the observed half life in Cu-58 , we propose shape mixing of the final state.

  • 17. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Systematics of proton emission2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, no 7, p. 072501-Article in journal (Refereed)
    Abstract [en]

    A very simple formula is presented that relates the logarithm of the half-life, corrected by the centrifugal barrier, with the Coulomb parameter in proton decay processes. The corresponding experimental data lie on two straight lines which appear as a result of a sudden change in the nuclear shape marking two regions of deformation independently of the angular momentum of the outgoing proton. This feature provides a powerful tool to assign experimentally quantum numbers in proton emitters.

  • 18. Delion, D. S.
    et al.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Theories of proton emission2006In: Physics reports, ISSN 0370-1573, E-ISSN 1873-6270, Vol. 424, no 3, p. 113-174Article, review/survey (Refereed)
    Abstract [en]

    Proton emission studies are presently the focal point of nuclear structure as well as nuclear reaction investigations in rare nuclei. Theoretical approaches to investigate the properties of such nuclei by using proton emission are reviewed. We analyse time-dependent and stationary formalisms within adiabatic and non-adiabatic methods. We investigate and compare the use of resonant Gamow states within coupled channels, R-matrix and distorded wave approaches. We give a description of odd-even as well as odd-odd proton emitters using axially symmetric or triaxial potentials. The emission to excited states of the daughter nucleus and angular distribution of the emitted proton is discussed. The status of numerical applications for both spherical and deformed approaches is reviewed. The importance of proton emission in analysing the properties of nuclear matter under exotic conditions is emphasized. in the appendices we give all technical details necessary to compute the observables connected with proton emission.

  • 19.
    Delion, D. S.
    et al.
    Horia Hulubei Natl Inst Phys & Nucl Engn, Romania.
    Patial, Monika
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    A simple approach to alpha-decay fine structure2016In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 43, no 9, article id 095109Article in journal (Refereed)
    Abstract [en]

    We propose a simple method to evaluate alpha-transition rates to low-lying excited states in even-even nuclei. For this a realistic alpha-daughter doublefolding interaction is approximated by a parabola in the region where the decay process takes place. This allows us to evaluate the penetration probability analytically. The main experimental features of branching ratios to excited states are reproduced by this simple approach.

  • 20. Delion, D. S.
    et al.
    Wyss, Ramon
    KTH, Superseded Departments, Physics.
    Karlgren, Daniel
    KTH, Superseded Departments, Physics.
    Liotta, Roberto
    KTH, Superseded Departments, Physics.
    Proton emission from triaxial nuclei2004In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 70, no 6, p. 061301-Article in journal (Refereed)
    Abstract [en]

    Proton decay from triaxially deformed nuclei is investigated. The deformation parameters corresponding to the mother nucleus are determined microscopically and the calculated decay widths are used to probe the mean-field wave function. The proton wave function in the mother nucleus is described as a resonant state in a coupled-channel formalism. The decay width, as well as the angular distribution of the decaying particle, are evaluated and their dependence upon the triaxial deformation parameters is studied in the decay of Re-161 and Bi-185. It is found that the decay width is very sensitive to the parameters defining the triaxial deformation while the angular distribution is a universal function which does not depend upon details of the nuclear structure.

  • 21. Delion, D. S.
    et al.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Sandzelius, Mikael
    KTH, School of Engineering Sciences (SCI), Physics.
    Investigations of proton-neutron correlations close to the drip line2010In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 82, no 2, p. 024307-Article in journal (Refereed)
    Abstract [en]

    Proton-neutron correlations in nuclei above the Z = 50 shell closure are investigated with the aim of understanding the behavior of the 2(+) and 4(+) states in Te and Xe isotopes, which remain at a rather constant energy as one approaches the shell closure at N = 50. Our calculations reveal that standard quasiparticle random phase approximation calculations, involving a quadrupole-quadrupole (QQ) interaction with constant strengths, cannot explain this feature. It is found that to reproduce the experimental data within this model one has to include a variable proton-neutron interaction. It turns out that an increased proton-neutron QQ interaction increases the collectivity (i.e., B(E2) values) when approaching the N = 50 region, whereas an increased proton-neutron pairing interaction decreases the collectivity. We thus conclude that the ratio between the B(E2) value and 2(+) energy is a "fingerprint" of proton-neutron collectivity and it should be determined in future experiments concerning light Te isotopes. Based on this criterion, we conclude that the available experimental data indicate an enhanced proton-neutron pairing interaction by approaching doubly magic Z = N = 20 and Z = N = 28 regions.

  • 22. Dussel, G. G.
    et al.
    Betan, R. Id
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Vertse, T.
    Collective excitations in the continuum2009In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 80, no 6, p. 064311-Article in journal (Refereed)
    Abstract [en]

    Pairing (particle-particle) giant resonances are analyzed within a shell-model formalism in the complex energy plane with the aim of understanding why they have not been observed so far. A comparison is made with the equivalent particle-hole mode by applying the formalism to the analysis of the well-understood particle-hole giant resonance. It is found that because of the proper treatment of the continuum intrinsic to the formalism, giant pairing resonances lie much higher than previously predicted and that some of them may be too wide to be observed, whereas others are meaningful excitations. For these, new experimental searches are proposed.

  • 23. Dussel, G. G.
    et al.
    Betan, R. Id
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics.
    Vertse, T.
    One- and two-quasiparticle states in the complex energy plane2007In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 789, p. 182-200Article in journal (Refereed)
    Abstract [en]

    One- and two-quasi particle states are studied in the complex energy plane. It is found that the pairing interaction does not change the character of the complex state. If a normal state is a physically meaningful resonance, then it will remain as such throughout the shell and if it is unphysical it will also remain as such throughout the shell. An important consequence of this is that it justifies the use of bound representations to evaluate many-body systems within the shell-model in cases where the single-particle states are narrow resonances. The character of two-quasiparticle states may oscillate between meaningful resonances and unphysical complex excitations as the number of particles increases.

  • 24.
    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.

  • 25.
    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)
  • 26.
    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.

  • 27.
    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.

  • 28.
    Hadinia, Baharak
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Cederwall, Bo
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Joss, Dave
    CCLRC, Daresbury Laboratory, Warrington.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Page, Robert
    Oliver Lodge Laboratory, Department of Physics, University of Liverpool.
    Johnson, Arne
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Lagergren, Karin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Ganioğlu, Ela
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Andgren, Karin
    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.
    Sandzelius, Mikael
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    et al.,
    In-beam gamma-ray and alpha-decay spectroscopy of 170Ir2007In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 76, no 4, p. 044312-1-044312-8Article in journal (Refereed)
    Abstract [en]

    Excited states in the highly neutron deficient odd-odd nucleus Ir-170 have been investigated. The experiment was performed using the Sn-112(Ni-60, pn)Ir-170 reaction and employing the recoil-decay tagging technique. Gamma rays were detected using the JUROGAM gamma-ray spectrometer and those belonging to Ir-170 were selected based on recoil identification provided by the RITU gas-filled recoil separator and the GREAT spectrometer at the RITU focal plane. A partial level scheme of Ir-170 is presented for the first time. New alpha-decay branches are assigned to Ir-170 and a tentative level structure for Re-166 is deduced from a study of the alpha-decay fine structure and the associated alpha-gamma correlations.

  • 29.
    Hadinia, Baharak
    et al.
    KTH, Superseded Departments, Physics.
    Cederwall, Bo
    KTH, Superseded Departments, Physics.
    Lagergren, Karin
    KTH, Superseded Departments, Physics.
    Blomqvist, Jan
    KTH, Superseded Departments, Physics.
    Bäck, Torbjörn
    KTH, Superseded Departments, Physics.
    Johnson, Arne
    KTH, Superseded Departments, Physics.
    Liotta, Roberto
    KTH, Superseded Departments, Physics.
    et al.,
    First identification of gamma-ray transitions in 107Te2004In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 70, no 6, p. 064314-1-064314-4Article in journal (Refereed)
    Abstract [en]

    Gamma-ray transitions in Te-107 have been identified for the first time. The experiment, which utilized the recoil decay tagging technique, was performed at the accelerator laboratory of the University of Jyvaskyla, Finland. Prompt gamma rays produced in Ni-58(Cr-52,3n)Te-107(*) reactions were detected by the JUROGAM gamma-ray spectrometer. The gamma rays belonging to Te-107 were selected based on the recoil identification provided by the RITU gas-filled recoil separator and the GREAT focal plane spectrometer. A first excited state at 90 keV, tentatively of g(7/2) character, is proposed.

  • 30. Id Betan, R.
    et al.
    Dussel, G. G.
    Liotta, Roberta
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Assessment of the importance of the pairing interaction in the continuum2008In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 78, no 4, p. 044325-Article in journal (Refereed)
    Abstract [en]

    A pairing interaction fitted to be applied in nuclei with active particles moving close to the continuum threshold or even immersed in the continuum itself is introduced. It is found that the effects of the nonresonant continuum upon physically meaningful quantities is unimportant. We applied the theory to heavy tin isotopes and good agreement between theory and the very few available experimental data is found.

  • 31.
    Id Betan, Rodolfo M.
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Liotta, Robert J.
    KTH, School of Engineering Sciences (SCI), Physics.
    Sandulescu, Neculai
    KTH, School of Engineering Sciences (SCI), Physics.
    Vertse, Tamas
    KTH, School of Engineering Sciences (SCI), Physics.
    Complex shell model with antibound states2005In: Key Topics in Nuclear Structure / [ed] Covello, A, 2005, p. 91-101Conference paper (Refereed)
    Abstract [en]

    An unified shell model scheme to evaluate simultaneously the contributions of bound single-particle states, Gamow resonances, antibound (virtual) states and continuum complex scattering states is presented. The formalism could be very suitable to study processes occurring in the continuum part of the nuclear spectra.

  • 32.
    Id Betan, Rodolfo M
    et al.
    KTH, Superseded Departments, Physics.
    Liotta, Roberto J.
    KTH, Superseded Departments, Physics.
    Sandulescu, Neculai
    KTH, Superseded Departments, Physics.
    Vertse, Tamas
    KTH, Superseded Departments, Physics.
    Two-particle resonances in the complex energy plane2004In: Few-body systems, ISSN 0177-7963, E-ISSN 1432-5411, Vol. 34, no 1-3, p. 51-56Article in journal (Refereed)
    Abstract [en]

    An evaluation of two-particle resonances in the complex energy plane is presented. The representation used in the method consists of bound and antibound single-particle states, Gamow resonances and scattering waves on the complex energy plane. Within this representation the structure of halo nuclei is studied.

  • 33.
    Id Betan, Rodolfo M
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Sandulescu, N.
    Vertse, T.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Complex shell model representation including antibound states2005In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 72, no 5, p. 054322-Article in journal (Refereed)
    Abstract [en]

    A generalization of the complex shell model formalism is presented that includes antibound states in the basis. These states, together with bound states, Gamow states, and the continuum background, represented by properly chosen scattering waves, form a representation in which all states are treated on the same footing. Two-particle states are evaluated within this formalism, and observable two-particle resonances are defined. The formalism is illustrated in the well-known case of Li-11 in its bound ground state and in Ca-70(g.s.), which is also bound. Both cases are found to have a halo structure. These halo structures are described within the generalized complex shell model. We investigated the formation of two-particle resonances in these nuclei, but no evidence of such resonances was found.

  • 34.
    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.

  • 35.
    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.

  • 36.
    Karlgren, Daniel
    et al.
    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.
    Huyse, M.
    Van de Vel, K.
    Van Duppen, P. B
    Alpha-decay hindrance factors: A probe of mean-field wave function2006In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 73, no 6, p. 064304-Article in journal (Refereed)
    Abstract [en]

    A simple model to calculate alpha-decay hindrance factors (HF) with special emphasis on the shape coexistence in the Pb-Po region is presented. Using deformation values obtained from potential energy surface (PES) calculations as the only input, hindrance factors for the alpha decay of Rn and Po isotopes are calculated. The fair agreement between experimental and theoretical hindrance factors suggest that the wave function obtained from the energy minima of the PES calculations contains an important part of the correlations that play a role for the alpha decay. The model is applicable to shape coexistence in the Po and Pb region when minima are well defined. The calculated HF that emerge from these calculations render a different interpretation than the commonly assumed n-particle n-hole picture of the intruder states in the Pb region.

  • 37.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Aurel sandulescu - A life dedicated to nuclear physics2013In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 413, no 1Article in journal (Refereed)
    Abstract [en]

    I was surprised to receive an invitation letter from Andrei Dorobantu, whom I did not know, to give a talk about pairing excitations at the Predeal International School of 1978, which I accepted. This was the first time that I would visit Romania, and I knew very little about the research that was performed in the country.

    In my talk I was showing the role of the pairing mode in a rather popular theory at that time which was called Nuclear Field Theory. Suddenly I was interrupted in a rather brusque fashion by a man with an acute and loud voice, telling me that it has been shown by somebody that the Nuclear Field Theory does not converge. I was very upset by this interruption, particularly because he was right. I told him this and asked him to wait up at the end of my talk. During the coffee break the man came to me and presented himself. It was the first time I came into contact with the extraordinary person that is Aurel Sandulescu.

    During the coffee break we spoke about his research, especially in alpha decay. I was interested in this subject because just then I had started to perform calculations in relation to experiments carried out at my Institution in Stockholm, which at that time was called the Research Institute of Physics.

    We continued with our discussions during the whole duration of the School, often with his wife, Violeta, present. I became amazed by the extensive work he had done since the late 1950s on microscopic treatments of alpha decay. He had studied the decay of both normal and superfluid as well as spherical and deformed nuclei, all within the framework of the shell model or its BCS equivalent. I was very enthusiastic about this, since I was convinced that one should, in principle, be able to describe the decay process by using a shell model representation. I was disappointed to realize that he did not agree with me. I insisted that from a purely theoretical point of view the shell model was, rather more than a model, an excellent representation to describe nuclear processes. However, with the perspective that the passing years provides, I have since had to admit that one needs cluster components in the shell model wave functions in order to properly describe the clustering and subsequent decay. For Aurel, this realization led him to consider the decay as a fission process. It was through this that he found, just by simply looking through the penetrability, that cluster radioactivity is a valid form of decay, as was indeed confirmed experimentally several years afterwards. This new form of radioactive decay has had a profound influence on nuclear physics. It opened the way to the investigation of the structure and exotic forms that superheavy nuclei may acquire, since one expects that heavy clusters are likely to be emitted from these nuclei. The importance of cluster decay, and the theory behind its discovery, is of great relevance even today. This can be attested, for example, by the recent prediction of Poenaru, Gherghescu and Greiner (2011 Phys. Rev. Lett 107 062503) that in some superheavy nuclei this form of decay is dominant even over alpha emission, thus making cluster decay a powerful tool in the detection of superheavy nuclei.

    The description of cluster decay as a fragmentation process and its relation to heavy and superheavy elements was a natural extension of the research that Aurel Sandulescu was conducting at that time. Just before the cluster decay paper appeared he addressed the important question of the production of superheavy elements. The straightforward method of reaching this is by heavy ions collisions, but the question was: which nuclei should one use as reaction partners? Sandulescu proposed choosing those nuclei that provide a minimum of the potential energy, which was an important step in the synthesis of superheavy nuclei.

    Another subject which is of great importance in nuclear physics and in which Sandulescu played a crucial role was his prediction of neutronless spontaneous binary and ternary fission. He was so elated and eager about this that he even contributed to the experimental discovery of this rare phenomenon. Since then, there have been many theoretical as well as experimental studies performed in this and similar subjects related to cold fission processes. Particularly relevant in the framework of this conference are his studies on the damping of collective modes in deep inelastic collisions. He treated this difficult subject by extending a formalism derived for open systems to nuclear collective motions. The master equation that he thus obtained describes well the dynamics of degrees of freedom not only in the damping of excited nuclear states, but also particularly in heavy ion collisions and in the decaying of the most collective states in nuclear physics—giant resonances.

    He has also analyzed the complicated mechanisms that induce the clustering of nucleons, which led to his realization that the cluster structure can be viewed as solitons moving on the nuclear surface.

    This intense scientific work was followed by other related activities. In Romania he became a full professor in 1970, a corresponding member of the Romanian Academy of Sciences in 1991, an ordinary member in 1992 and Vice President in the period 1994–1998. Most remarkable is that he tried to influence the development of Science in the country by himself becoming a politician. Thus, he was a member of the Romanian Parliament in the period 1996–2000. Outside of Romania he has also undertaken remarkable activities. He has been Invited Scientist and Invited Professor to many institutions around the world. One should mention in particular his position as Vice Director of the Joint Institute of Nuclear Research, Dubna, Russia, in the period 1983–1986. He has proceeded through all these endeavors by attracting many foreign scientists to Romania, including myself. But especially important was his influence upon students, many of whom are today recognized physicists and leaders of Romanian physics.

    It is in recognition of his contribution to physics, especially nuclear physics, as well as his work for Romanian science that this School is organized in his honour, on the occasion of his 80th birthday.

    I cannot finish this short account without mentioning the person that accompanied Aurel Sandulescu through all his life, his wife of more than fifty years, Violeta. She also was an exceptional person. In her youth she was a very dedicated sporty girl, very athletic, very courageous, very fair and, above all, very generous. These qualities remained with her throughout her life. With deep sorrow I learnt that she passed away three months ago, still youthful and enthusiastic.

  • 38.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Developments in radioactive decay during the last Century2013In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 413, no 1, p. 012012-Article in journal (Refereed)
    Abstract [en]

    In this talk a review of the developments in radioactive decay processes that have taken place during the last Century, and the great outgrowths of these developments in Modern Physics, is presented.

  • 39. Patial, Monika
    et al.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    Microscopic description of superallowed alpha-decay transitions2016In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 93, no 5, article id 054326Article in journal (Refereed)
    Abstract [en]

    It was recently found that the formation probabilities of alpha particles in Te isotopes are larger than the corresponding probabilities in Po isotopes. We have done a full microscopic calculation within the framework of the multistep shell model to analyze in detail the formation probabilities and subsequent decays of alpha particles from Po-212 and Te-104. We have also calculated the spectra of these two decaying nuclei and found that the tentatively assigned spin (18(+)) at 2.922 MeV in Po-212 (National Nuclear Data Center, www.nndc.bnl.gov) is predicted to be a state 16(+). We also present for the first time the full energy spectrum of Te-104. The evaluated formation amplitudes in both nuclei show that in Te-104 there is indeed a superallowed alpha-decay transition.

  • 40. 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.

  • 41. 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.

  • 42.
    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.

  • 43.
    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.

  • 44.
    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.

  • 45.
    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.

  • 46.
    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, Nuclear 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.
    Spin-aligned neutron-proton pair mode in atomic nuclei2011In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 84, no 2, p. 021301-Article in journal (Refereed)
    Abstract [en]

    Shell-model calculations using realistic interactions reveal that the ground and low-lying yrast states of the N = Z nucleus (92)(46)Pd are mainly built upon isoscalar neutron-proton pairs, each carrying the maximum angular momentum J = 9 allowed by the shell 0g(9/2), which is dominant in this nuclear region. This structure is different from that found in the ground and low-lying yrast states of all other even-even nuclei studied so far. The low-lying spectrum of excited states generated by such correlated neutron-proton pairs has two distinctive features: (i) the levels are almost equidistant at low energies and (ii) the transition probability I -> I - 2 is approximately constant and strongly selective. This unique mode is shown to replace normal isovector pairing as the dominant coupling scheme in N = Z nuclei approaching the doubly magic nucleus (100)Sn.

  • 47.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Delion, Doru S.
    Liotta, Roberto J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Effects of formation properties in one-proton radioactivity2012In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 85, no 1, p. 011303-Article in journal (Refereed)
    Abstract [en]

    It is shown that the proton formation probability, extracted from experimental data corresponding to one-proton radioactivity, is divided into two regions when plotted as a function of an universal parameter. This parameter is derived from a microscopic description of the decay process. In this way we explain the systematics of proton emission half-lives. At the same time the formation probability is shown to be a useful quantity to determine the deformation property of the mother nucleus.

  • 48.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    NUCLEAR CLUSTERING AND GENERALIZATION OF THE GEIGER-NUTTALL LAW2012In: Romanian Journal of Physics, ISSN 1221-146XArticle in journal (Refereed)
  • 49.
    Qi, Chong
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear 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.
    Competition of different coupling schemes in atomic nuclei2012In: Advanced Many-Body And Statistical Methods In Mesoscopic Systems, Institute of Physics Publishing (IOPP), 2012, Vol. 338, no 012027, p. 012027-Conference paper (Refereed)
    Abstract [en]

    Shell model calculations reveal that the ground and low-lying yrast states of the N = Z nuclei Pd-92(46) and Cd-96 are mainly built upon isoscalar spin - aligned neutron - proton pairs each carrying the maximum angular momentum J = 9 allowed by the shell 0g(9)/(2) which is dominant in this nuclear region. This mode of excitation is unique in nuclei and indicates that the spin - aligned pair has to be considered as an essential building block in nuclear structure calculations. In this contribution we will discuss this neutron - proton pair coupling scheme in detail. In particular, we will explore the competition between the normal monopole pair coupling and the spin - aligned coupling schemes. Such a coupling may be useful in elucidating the structure properties of N = Z and neighboring nuclei.

  • 50.
    Qi, Chong
    et al.
    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.
    Generalization of the Geiger-Nuttall law and alpha clustering in heavy nuclei2012In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 381, p. 012131-Article in journal (Refereed)
    Abstract [en]

    A generalization of the Geiger-Nuttall law is deduced, which is valid for the radioactivity of all clusters (including alpha particles), by considering the clusterization and subsequent decay of nucleons within the nucleus. This universal decay law (UDL) is a linear relation between the half-lives of the decaying clusters and the corresponding Q-values. In this universal decay law (UDL) the penetrability is still a dominant quantity. By using three free parameters only, one finds that all known ground state to ground state radioactive decays are explained rather well. This allows us to search for new cluster decay modes and to carry out a simple and model-independent study of the decay properties of nuclei over the whole nuclear chart. It also helps in distinguishing the role played by pairing collectivity in the clustering process in heavy nuclei.

12 1 - 50 of 62
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