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  • 1. Boso, A.
    et al.
    Lenzi, S. M.
    Recchia, F.
    Bonnard, J.
    Aydin, S.
    Bentley, M. A.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Clement, E.
    De France, G.
    Di Nitto, A.
    Dijon, A.
    Doncel, Maria
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Gottardo, A.
    Henry, T.
    Huyuk, T.
    Jaworski, G.
    John, P. R.
    Juhasz, K.
    Kuti, I.
    Melon, B.
    Mengoni, D.
    Michelagnoli, C.
    Modamio, V.
    Napoli, D. R.
    Nyako, B. M.
    Nyberg, J.
    Palacz, M.
    Valiente-Dobon, J. J.
    ISOSPIN SYMMETRY BREAKING IN MIRROR NUCLEI Mg-23-Na-232017Inngår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 48, nr 3, s. 313-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mirror energy differences (MED) are a direct consequence of isospin symmetry breaking. Moreover, the study of MED has proved to give valuable information of several nuclear structure properties. We present the results of an experiment performed in GANIL to study the MED in mirror nuclei Mg-23-Na-23 up to high spin. The experimental values are compared with state-of-the-art shell model calculations. This permits to enlighten several nuclear structure properties, such as the way in which the nucleons alignment proceeds, the radius variation with J, the role of the spin-orbit interaction and the importance of isospin symmetry breaking terms of nuclear origin.

  • 2.
    Bäck, Torbjörn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Wyss, Ramon
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Wadsworth, R.
    Transition probabilities near Sn-100 and the stability of the N, Z=50 shell closure2013Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 87, nr 3, s. 031306-Artikkel i tidsskrift (Fagfellevurdert)
    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, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Moradi, Farnaz Ghazi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Wyss, Ramon
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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 technique2012Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T150, s. 014003-Artikkel i tidsskrift (Fagfellevurdert)
    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, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Wyss, Ramon
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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)Te2011Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 84, nr 4, s. 041306-Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Cederwall, Bo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Blomqvist, Jan-Erik
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Lagergren, Karin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Dijon, A.
    Grand Accélérateur National d´lons Lourds, Cean Cedex, France.
    Jaworski, G.
    Heavy Ion Laboratory, Univeristy of Warsaw, Warsaw, Poland.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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, Skolan för teknikvetenskap (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, Skolan för teknikvetenskap (SCI), Fysik.
    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, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Recchia, F.
    Dipartimento di Fisica dell'Universitá di Padova and Instituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova, Italy.
    Sandzelius, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    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 92Pd2011Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 469, nr 7328, s. 68-71Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 6.
    Ertoprak, Aysegul
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik. Istanbul University Vezneciler/Fatih, Istanbul, Turkey.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Jakobsson, U.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Nyako, B. M.
    Nyberg, J.
    Davies, P.
    Doncel, Maria
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    De France, G.
    Kuti, I.
    Napoli, D. R.
    Wadsworth, R.
    Ghugre, S. S.
    Raut, R.
    Akkus, B.
    Al-Azri, H.
    Algora, A.
    de Angelis, G.
    Atac, A.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Boso, A.
    Clement, E.
    Debenham, D. M.
    Dombradi, Zs.
    Erturk, S.
    Gadea, A.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Gottardo, A.
    Huyuk, T.
    Ideguchi, E.
    Jaworski, G.
    Li, H.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Michelagnoli, C.
    Modamio, V.
    Palacz, M.
    Petrache, C. M.
    Recchia, F.
    Sandzelius, M.
    Siciliano, M.
    Timar, J.
    Valiente-Dobon, J. J.
    Xiao, Z. G.
    LIFETIME MEASUREMENTS WITH THE DOPPLER SHIFT ATTENUATION METHOD USING A THICK HOMOGENEOUS PRODUCTION TARGET - VERIFICATION OF THE METHOD2017Inngår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 48, nr 3, s. 325-329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Doppler Shift Attenuation Method (DSAM) analysis of excited-state lifetimes normally employs thin production targets mounted on a thick stopper foil ("backing") serving to slow down and stop the recoiling nuclei of interest in a well-defined manner. Use of a thick, homogeneous production target leads to a more complex analysis as it results in a substantial decrease in the energy of the incident projectile which traverses the target with an associated change in the production cross section of the residues as a function of penetration depth. Here, a DSAM lifetime analysis using a thick homogeneous target has been verified using the Doppler broadened lineshapes of gamma rays following the decay of highly excited states in the semi-magic (N = 50) nucleus Ru-94. Lifetimes of excited states in the Ru-94 nucleus have been obtained using a modified version of the LINESHAPE package from the Doppler broadened lineshapes resulting from the emission of the gamma rays, while the residual nuclei were slowing down in the thick (6 mg/cm(2)) metallic Ni-58 target. The results have been validated by comparison with a previous measurement using a different (RDDS) technique.

  • 7.
    Ertoprak, Aysegul
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik. Istanbul University Vezneciler/Fatih, Istanbul, Turkey.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Doncel, Maria
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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 94RuManuskript (preprint) (Annet vitenskapelig)
    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.

  • 8.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Experimental Nuclear Structure Studies in the Vicinityof the N = Z Nucleus 100Sn and in the ExtremelyNeutron Deficient 162Ta Nucleus2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This work covers spectroscopic studies of nuclei from different regions of the Segré chart whose properties illustrate the delicate balance between the forces in the atomic nucleus. Studies of nuclei far from stability offer new insights into the complex nucleon many-body problem. In nuclei with equal neutron and proton numbers (N = Z), the unique nature of the atomic nucleus as an object composed of two distinct types of fermions can be expressed as enhanced correlations arising between neutrons and protons occupying orbitals with the same quantum numbers. The bound N = Z nuclei with mass number A > 90 can only be produced in the laboratory at very low cross sections. The related problems of identifying and distinguishing such reaction products and their associated gamma rays have prevented a firm interpretation of their structure even for the lowest excited states until recently. In the present work the experimental difficulties of observation of excited states in the N = Z = 46 nucleus 92Pd have been overcome through the use of a highly efficient, state-of-the-art detector system; the EXOGAM-Neutron Wall-DIAMANT setup, and a prolonged experimental running period. The level spacings in the ground state band of 92Pd give the first experimental evidence for a new spin-aligned neutron-proton (np) paired phase, an unexpected effect of enhanced np correlations for N = Z nuclei in the immediate vicinity of the doubly magic nucleus 100Sn.

    Excited states in 94Ru and 95Rh nuclei close to the double magic shell  Z = N = 50 have been studied in order to untangle the ambiguity of the spin and the parity of the lowest-lying states. The observed yrast structures are compared to results of large-scale shell model (LSSM) calculations and the strengths of hindered E1 transitions are used as a sensitive test of the LSSM parameters. The effect of single-particle-hole excitations is discussed in terms of the strength of hindered E1 transitions.

    Excited states of the odd-odd nucleus 162Ta have been observed using the JUROGAM/RITU experimental set-up. This nucleus is located in a transitional region in the nuclide chart which is between near-spherical nuclei and well-deformed nuclei, offering the possibility to study the emergence of collective phenomena and nuclear deformation (in particular the degree of triaxiality). The results, which are interpreted in the framework of the cranked shell model with total Routhian surface calculations, suggest an almost axially symmetric nuclear shape. The energy staggering between the signature partners of the yrast rotational bands has been deduced for eight odd-odd isotopes in the neighborhood of 162Ta nucleus and the special observed feature of signature inversion for these nuclei is discussed.

  • 9.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    In-Beam Spectroscopy of the Neutron Deficient Nuclei 92Pd and 162Ta2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Studies of nuclei far from stability offers new insights into the complete nucleon many-body problem. In nuclei with equal neutron and proton numbers (N=Z), the unique nature of the atomic nucleus as an object composed of two distinct types of fermions can be expressed as enhanced correlations arising between neutrons and protons occupying orbitals with the same quantum numbers. Such correlations have since several decades been predicted to favour a new type of nuclear superfluidity; isoscalar neutron-proton pairing, in addition to normal isovector pairing which dominates the structure of most known nuclei. Despite many experimental efforts these predictions have not been confirmed. The N=Z nuclei with mass number A>90 can only be produced in the laboratory at very low cross sections. The related problems of identifying and distinguishing such reaction products and their associated gamma rays from the vast array of N>Z nuclei that are present in much greater numbers have prevented observation of their low-lying excited states until recently. In the present work the experimental difficulties of observation of excited states in the N=Z=46 nucleus 92Pd have been overcome through the use of a highly efficient, state-of-the-art detector system and a prolonged experimental running period. The lowest excited states in 92Pd was empirically observed via detection of gamma rays emitted in the fusion-evaporation reaction together with detection of charged particles and neutrons in the ancillary detector system. The level spacings in the ground state band of 92Pd give the first experimental evidence for a new spin-aligned neutron-proton (np) paired phase. These findings reconcile with nuclear shell model calculations which predicts an unexpected effect of enhanced np correlations for N=Z nuclei in the immediate vicinity of the doubly magic nucleus 100Sn. Excited states of the odd-odd nucleus 162Ta have been observed using the JUROGAM/RITU experimental set-up. This nucleus is located in a transitional region in the nuclide chart which is between near-spherical nuclei and well-deformed nuclei, offering the possibility to study the emergence of collective phenomena and nuclear deformation (in particular the degree of triaxiality). The results, which are interpreted in the framework of the cranked shell model with total Routhian surface calculations suggest an almost axially symmetric nuclear shape. The energy staggering between the signature partners of the yrast rotational bands has been deduced for eight odd-odd isotopes in the neighborhood of 162Ta nucleus and the special observed feature of signature inversion for these nuclei is discussed.

     

  • 10.
    Ghazi Moradi, Farnaz
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Sandzelius, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Atac, Ayse
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Hadinia, Baharak
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Andgren, Karin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Khaplanov, Anton
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Wyss, Ramon
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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 162Ta2011Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 84, nr 6, s. 064312-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Ghazi Moradi, Farnaz
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ataç, Ayşe
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Doncel, Maria
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    et al.,
    Spectroscopy of the neutron deficient N=50 nucleus 95Rh2014Manuskript (preprint) (Annet vitenskapelig)
  • 12.
    Ghazi Moradi, Farnaz
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ataç, Ayşe
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Doncel, Maria
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    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-952014Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 89, nr 4, s. 044310-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 13.
    Ghazi Moradi, Farnaz
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Qi, Chong
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ataç, Ayşe
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Liotta, Roberto
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Doncel, Maria
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Johnson, Arne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    et al.,
    Character of particle-hole excitations in Ru-94 deduced from gamma-ray angular correlation and linear polarization measurements2014Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 89, nr 1, s. 0143011-0143019Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 14. Ralet, D
    et al.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Doncel, Maria
    KTH.
    Ghazi Moradi, Farnaz
    KTH.
    Zielinska, M.
    et al.,
    Lifetime measurement of neutron-rich even-even molybdenum isotopes2017Inngår i: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 95, nr 3, artikkel-id 034320Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: In the neutron-rich A approximate to 100 mass region, rapid shape changes as a function of nucleon number as well as coexistence of prolate, oblate, and triaxial shapes are predicted by various theoretical models. Lifetime measurements of excited levels in the molybdenum isotopes allow the determination of transitional quadrupole moments, which in turn provides structural information regarding the predicted shape change. Purpose: The present paper reports on the experimental setup, the method that allowed one to measure the lifetimes of excited states in even-even molybdenum isotopes from mass A = 100 up to mass A = 108, and the results that were obtained. Method: The isotopes of interest were populated by secondary knock-out reaction of neutron-rich nuclei separated and identified by the GSI fragment separator at relativistic beam energies and detected by the sensitive PreSPEC-AGATA experimental setup. The latter included the Lund-York-Cologne calorimeter for identification, tracking, and velocity measurement of ejectiles, and AGATA, an array of position sensitive segmented HPGe detectors, used to determine the interaction positions of the gamma ray enabling a precise Doppler correction. The lifetimes were determined with a relativistic version of the Doppler-shift-attenuation method using the systematic shift of the energy after Doppler correction of a gamma-ray transition with a known energy. This relativistic Doppler-shift-attenuation method allowed the determination of mean lifetimes from 2 to 250 ps. Results: Even-even molybdenum isotopes from mass A = 100 to A = 108 were studied. The decays of the low-lying states in the ground-state band were observed. In particular, two mean lifetimes were measured for the first time: tau = 29.7(-9.1)(+11.3) ps for the 4(+) state of Mo-108 and tau = 3.2(-0.7)(+ 0.7) ps for the 6(+) state of Mo-102. Conclusions: The reduced transition strengths B(E2), calculated from lifetimes measured in this experiment, compared to beyond-mean-field calculations, indicate a gradual shape transition in the chain of molybdenum isotopes when going from A = 100 to A = 108 with a maximum reached at N = 64. The transition probabilities decrease for Mo-108 which may be related to its well-pronounced triaxial shape indicated by the calculations.

  • 15. Zheng, Y.
    et al.
    de France, G.
    Clement, E.
    Dijon, A.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Wadsworth, R.
    Bäck, Torbjörn
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Ghazi Moradi, Farnaz
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Jaworski, G.
    Nyako, B. M.
    Nyberg, J.
    Palacz, M.
    Al-Azri, H.
    de Angelis, G.
    Atac, A.
    Aktas, O.
    Bhattacharyya, S.
    Brock, T.
    Davies, P. J.
    Di Nitto, A.
    Dombradi, Zs.
    Gadea, A.
    Gal, J.
    Joshi, P.
    Juhasz, K.
    Julin, R.
    Jungclaus, A.
    Kalinka, G.
    Kownacki, J.
    La Rana, G.
    Lenzi, S. M.
    Molnar, J.
    Moro, R.
    Napoli, D. R.
    Singh, B. S. Nara
    Persson, Andreas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Recchia, F.
    Sandzelius, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Scheurer, J. -N
    Sletten, G.
    Sohler, D.
    Söderstrom, P. -A
    Taylor, M. J.
    Timar, J.
    Valiente-Dobon, J. J.
    Vardaci, E.
    gamma-ray linear polarization measurements and (g(9/2))(-3) neutron alignment in Ru-912013Inngår i: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 87, nr 4, s. 044328-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Linear polarization measurements have been performed for gamma rays in Ru-91 produced with the Ni-58(Ar-36,2p1n gamma)Ru-91 reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the gamma-gamma coincidences, gamma-ray linear polarization, and gamma-ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3-1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in Ru-91. More specifically, calculations using a semiempirical shell model were performed to understand the structures of the first and second (21/2(+)) and (17/2(+)) levels. The results are in good agreement with the experimental data, supporting the interpretation of the nonyrast (21/2(+)) and (17/2(+)) states in terms of the J(max) and J(max) - 2 members of the seniority-three nu(g(9/2))(-3) multiplet.

1 - 15 of 15
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