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1.
  • Svensson, C. E., et al. (författare)
  • Decay Out of the Doubly Magic Superdeformed Band in the N=Z Nucleus 60Zn
  • 1999
  • Ingår i: Physical Review Letters. - 1079-7114. ; 82:17, s. 3400-3403
  • Tidskriftsartikel (refereegranskat)abstract
    • The doubly magic superdeformed band in the N = Z nucleus Zn-60 has been identified. Linking transitions connecting this band to the yrast line provide the first spin, parity, and excitation energy measurements for superdeformed states in the A similar to 60 region. The stretched-E2 character and relatively large B(E2) values of these transitions suggest a nonstatistical decay-out process.
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2.
  • Gellanki, Jnaneswari, et al. (författare)
  • Characterization of Superdeformed Bands in 62Zn
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Combined data from four fusion-evaporation reaction experiments were utilized to investigate deformed and superdeformed structures in Zn-62(30)32. Combination of the Gammasphere gamma-ray spectrometer and ancillary particle detection systems allowed for the connection of rotational bands to well-known, low-lying excited states in Zn-62, as well as spectroscopy of discrete high-spin states reaching excitation energies of E-x=42.5 MeV. Four well- or superdeformed bands in Zn-62 are characterized and described by means of cranked Nilsson-Strutinsky calculations.
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3.
  • Svensson, C. E., et al. (författare)
  • Collective rotational motion in the N=Z nucleus 36Ar
  • 2001
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 682:1-4, s. 1-11
  • Tidskriftsartikel (refereegranskat)abstract
    • A superdeformed rotational band has been identified in the N = Z nucleus 36Ar, firmly linked to known low-spin states, and observed to its high-spin termination at Iπ = 16+. Lifetime measurements by the Doppler shift attenuation method establish a large low-spin deformation (β2 ≈ 0.46) and a decrease in the collectivity as the band approaches termination. Comparisons with cranked Nilsson-Strutinsky and large-scale spherical shell model calculations lead to a consistent description of the band based on a configuration in which four particles are promoted to the pf shell. With two major shells active for both protons and neutrons, yet a valence space dimension small enough to be approached from the shell model perspective, this band offers an excellent opportunity to investigate the microscopic structure of collective rotational motion in nuclei.
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4.
  • Svensson, C. E., et al. (författare)
  • Smooth Termination of Rotational Bands in 62Zn: Evidence for a Loss of Collectivity
  • 1998
  • Ingår i: Physical Review Letters. - 1079-7114. ; 80:12, s. 2558-2561
  • Tidskriftsartikel (refereegranskat)abstract
    • Two sets of strongly coupled rotational bands have been identified in Zn-62. These bands have been observed up to the terminating states of their respective configurations. Lifetime measurements indicate that the transition quadrupole moments in these bands decrease as termination is approached. These results establish the first terminating states of rotational bands in the A similar to 60 mass region and confirm the predicted loss of collectivity associated with smooth band termination.
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5.
  • Svensson, C. E., et al. (författare)
  • Superdeformation in the N = z Nucleus 36Ar : Experimental, deformed mean field, and spherical shell model descriptions
  • 2000
  • Ingår i: Physical Review Letters. - 0031-9007. ; 85:13, s. 2693-2696
  • Tidskriftsartikel (refereegranskat)abstract
    • A superdeformed rotational band has been identified in 36Ar, linked to known low-spin states, and observed to its high-spin termination at Iπ = 16+. Cranked Nilsson-Strutinsky and spherical shell model calculations assign the band to a configuration in which four pf-shell orbitals are occupied, leading to a low-spin deformation β2 ≈ 0.45. Two major shells are active for both protons and neutrons, yet the valence space remains small enough to be confronted with the shell model. This band thus provides an ideal case to study the microscopic structure of collective rotational motion.
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6.
  • Kelsall, N. S., et al. (författare)
  • Testing mean-field models near the N=Z line : gamma-ray spectroscopy of the T-z=1/2 nucleus Kr-73
  • 2002
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 65:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the N=Z+1 nucleus Kr-73 have been investigated using the Ca-40(Ar-36,2pn) and Ca-40(Ca-40,alpha2pn) reactions at 145 and 160 MeV, respectively. gamma rays were detected using the Gammasphere array and events were recorded in coincidence with charged-particle and neutron detectors. The three previously observed bands were extended to high spin, and a new unfavored positive-parity band has been observed. The alignment characteristics and decay properties of the bands are all consistent with large-deformation prolate rotation, with no clear evidence for oblate bands or shape coexistence. This is quite different from neighboring Kr-72,Kr-74, indicating a strong shape-stabilizing role for the valence neutron. The experimental results are compared to extended total Routhian surface, cranked Nilsson Strutinsky, and cranked relativistic mean-field calculations. The results suggest that the paired calculations lack some important physics. Neutron-proton correlations may be the missing ingredient. There is also evidence for an unusual band crossing in the negative-parity bands, which may indicate the presence of T=0 pairing correlations. At high spin all the models can reproduce the experimental data.
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7.
  • Ward, D., et al. (författare)
  • Band Structure of 68Ge
  • 2001
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 63:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The nucleus Ge-68 has been studied by gamma-ray spectroscopy following its population at high spin in the reaction Ca-40(S-32,4p) Ge-68. The reaction channel was selected with the Microball array and gamma rays were detected with the Gammasphere array. The level scheme is very complex, reflecting the many different, and presumably mixed, excitation modes in this nucleus. Nevertheless, there appear to be some simplifications in the spin range above 18 (h) over bar where we have identified a superdeformed band and several terminating bands. The results are compared with a cranked Nilsson-Strutinsky model without pairing.
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8.
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9.
  • Döring, J., et al. (författare)
  • Band terminations in the valence space of 86Zr
  • 2000
  • Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 61:3, s. 343101-343106
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in 86Zr up to 30+ and 27- were observed via the 58Ni(32S,4p) reaction at 135 MeV beam energy using the combined GAMMASPHERE and MICROBALL systems. Calculations performed with the configuration-dependent shell-correction approach show that these states are built from six g9/2 neutrons and at most four protons excited from the p1/2,p3/2,f5/2 subshells to the g9/2 subshell at small deformation. The highest observed states at 27- and 30+ are interpreted as band-terminating states with the latter having the highest spin available in the valence space for 86Zr.
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10.
  • Pfohl, J., et al. (författare)
  • Highly deformed rotational structures in 136Pm
  • 2000
  • Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:3, s. 313041-313045
  • Tidskriftsartikel (refereegranskat)abstract
    • Four highly deformed structures in the odd-odd nucleus 13661Pm75 were observed via the 105Pd(35Cl,2p2n) reaction at 180 and 173 MeV using the GAMMASPHERE γ-ray spectrometer and the Microball charged-particle detector array. Quadrupole moment measurements were performed on all of the bands. In contrast to lighter odd-Ζ Pm and Pr nuclei, bands based on the g9/2[404]9/2 proton orbital were not observed. Instead, the four observed sequences are assigned as a coupling of an i13/2 neutron with the low-Ω h11/2 and mixed d5/2g7/2 orbitals. Comparisons with neighboring highly deformed structures are discussed and cranked Nilsson-Strutinsky calculations for 136Pm are presented.
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11.
  • Sun, H., et al. (författare)
  • New Band Structures and an Unpaired Crossing in 78Kr
  • 1999
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 59:2, s. 655-664
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Kr-78 were studied using the Ni-58(Na-23,3p) reaction at 70 MeV and the Ni-58(Si-23,alpha 4p) reaction at 130 MeV. Prompt gamma-gamma coincidences were measured using the Pitt-FSU detector array and the GAMMASPHERE-MICROBALL array. Results from these experiments have led to 26 new excitation levels, some of which have been grouped into 3 new bands. Spins were assigned based on directional correlations of oriented nuclei. Two of the new negative-parity bands appear to form a signature-partner pair based on a two-quasineutron structure, in contrast to the previously known two-quasiproton negative-parity bands. A forking has been observed at the 24(+) state in the yrast band, which calculations suggest may result from an unpaired crossing. The available evidence suggests oblate shapes in the yrast band coexist with prolate shapes in the negative-parity bands. [S0556-2813(99)04602-6].
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12.
  • Sylvan, G N, et al. (författare)
  • Deformation driving intruder orbitals in Kr-77
  • 1997
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 56:2, s. 772-781
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Kr-77 were identified via analysis of prompt gamma-gamma coincidences in the Ni-58(Si-29,2 alpha 2p) reaction at 128 MeV at the Gammasphere facility. Evaporation channel selection was achieved using the 95 element Microball charged-particle detector. 27 new states and 42 new transitions were found, The positive-parity bands were confirmed and the alpha=-1/2 band extended to 39/2(+). The negative-parity signature pair was extended to 31/2(-) and 37/2(-). Two new high-lying negative-parity bands were found extending from a state of spin I = 15/2 and energy 2.6 MeV to 17.4 MeV at I = (55/2). The new bands appear highly deformed and become yrast at high spin. A three-quasiparticle structure based on deformation driving, low-K unique-parity and intruder orbitals is suggested for them.
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13.
  • Wadsworth, R., et al. (författare)
  • Evidence for shape coexistence at medium spin in Rb-76
  • 2011
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 701:3, s. 306-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Four previously known rotational bands in Rb-76 have been extended to moderate spins using the Gammasphere and Microball gamma ray and charged particle detector arrays and the Ca-40(Ca-40,3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g(9/2) particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape coexisting structures at medium spins. (C) 2011 Elsevier B.V. All rights reserved.
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14.
  • Wadsworth, R., et al. (författare)
  • Terminating states in the positive-parity structures of As 67
  • 2018
  • Ingår i: Physical Review C. - 2469-9985. ; 98:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The energy levels and γ-ray decay scheme of the positive-parity states in the Tz=12 nucleus As67 have been studied by using the Ca40(Ar36,2αp)As67 reaction at a beam energy of 145 MeV. Two new band structures have been identified which can be connected to the previously known levels. The results for these bands are compared with configuration-dependent cranked Nilsson-Strutinsky calculations. The good level of agreement between theory and experiment suggests that these structures can be interpreted in terms of configurations that involve three g92 particles and that both possess noncollective terminating states.
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15.
  • Andersson, T., et al. (författare)
  • High-spin States in the A=39 Mirror Nuclei 39Ca and 39K
  • 1999
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 6, s. 5-8
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states of the mass A = 39 mirror pair K-39 and Ca-39 were investigated via the fusion-evaporation reaction Si-28+O-16 at 125 MeV beam energy. The GAMMASPHERE array in conjunction with the 4 pi charged-particle detector array MICROBALL and neutron detectors was used to detect gamma rays in coincidence with evaporated light particles. The results of the first high-spin study of the T-z = -1/2 nucleus Ca-39 are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d(3/2)-1f(7/2) configuration space.
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16.
  • Andreoiu, Corina, et al. (författare)
  • Yrast Superdeformed Band in 59Cu
  • 2000
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 62:5, s. 513011-513015
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in 59Cu were populated using the fusion-evaporation reactions 28Si+40Ca at a beam energy of 125 MeV and 36Ar+28Si at a beam energy of 143 MeV. The Gammasphere array in conjunction with ancillary detector systems allowed for the identification of a superdeformed rotational band in 59Cu, which was firmly linked to low-spin yrast states. Using directional correlations of oriented states, a spin-parity assignment of Iπ = 25/2+ to the band head was possible. The average quadrupole moment of the band is measured to be Qt = (2.24±0.40) e b. The characteristics of the band are compared to neighboring nuclei and predictions of different mean-field theories.
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17.
  • Fischer, S. M., et al. (författare)
  • Alignment delays in the N = Z nuclei Kr-72, Sr-76, and Zr-80
  • 2001
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 8713:13
  • Tidskriftsartikel (refereegranskat)abstract
    • The ground state rotational bands of the N = Z nuclei Kr-72, Sr-76, and Zr-80 have been extended into the angular momentum region where rotation alignment of particles is normally expected. By measuring the moments of inertia of these bands we have observed a consistent increase in the rotational frequency required to start pair breaking, when compared to neighboring nuclei. Kr-72 shows the most marked effect. It has been widely suggested that these delayed alignments arise from np-pairing correlations. However, alignment frequencies are very sensitive to shape degrees of freedom and normal pairing, so the new experimental observations are still open to interpretation.
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18.
  • Ideguchi, E., et al. (författare)
  • Orbifold projection in supersymmetric QCD at N(f) ≤ N(c)
  • 2000
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 492:3-4, s. 369-375
  • Tidskriftsartikel (refereegranskat)abstract
    • Supersymmetric orbifold projection of N = 1 SQCD with relatively small number of flavors (N(f) ≤ N(c)) is considered. The purpose is to check whether orbifolding commutes with the infrared limit. On the one hand, one considers the orbifold projection of SQCD and obtains the low-energy description of the resulting theory. On the other hand, one starts with the low-energy effective theory of the original SQCD, and only then performs orbifolding. It is shown that at finite N(c) the two low-energy theories obtained in these ways are different. However, in the case of stabilized run-away vacuum these two theories are shown to coincide in the large N(c) limit. In the case of quantum modified moduli space, topological solitons carrying baryonic charges are present in the orbifolded low-energy theory. These solitons may restore the correspondence between the two theories provided that the soliton mass tends to zero in the large N(c) limit. (C) 2000 Elsevier Science B.V.
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19.
  • Lipoglavsek, M., et al. (författare)
  • First Observation of Excitation Across the 100Sn Core
  • 2001
  • Ingår i: Nuclear Physics, Section A. - 0375-9474. ; 682, s. 399-403
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states of nuclei near the doubly-magic nucleus Sn-100 were studied with the Ni-58+Cr-50 reaction. The experimental setup consisted of the GAMMASPHERE array augmented with light charged-particle and neutron detectors. Excited states were identified for the first time in the proton emitting nucleus Sb-105. Excitations across the N=Z=50 doubly closed shell were observed in Cd-99 and In-101. Some results of large-scale shell-model calculations are discussed.
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20.
  • O'Leary, C. D., et al. (författare)
  • Evidence for isovector neutron-proton pairing from high-spin states in N = Z 74Rb
  • 2003
  • Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 67:2, s. 213011-213015
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the odd-odd N = Z nucleus 3774Rb37 were studied using the 40Ca(40Ca,αnp) reaction. A previously observed odd-spin T = 0 band has been extended to Iπ = (31+) and an even-spin T = 0 band has been observed for the first time to Iπ = (22+); both have a π(g9/2)⊗ν(g9/2) structure. A strongly coupled low-spin T = 0, K = 3 band has been interpreted as being based upon a π[312]3/2 ⊗ ν[312]3/2 configuration. Cranked relativistic Hartree-Bogoliubov calculations, which are corrected for the t = 1 np-pair field by restoring isospin symmetry, reproduce the observed spectrum. These new results provide evidence for the existence of an isovector pair field that contains a neutron-proton component with the proper strength for ensuring isospin conservation.
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21.
  • Rudolph, Dirk, et al. (författare)
  • Shell-model Influence in the Rotational Nucleus 86Mo
  • 1996
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 54:1, s. 117-124
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Mo-86 were studied by means of the fusion evaporation reaction Ni-58(S-32,2p2n) Mo-86 at 135 MeV beam energy. Charged-particle-gamma gamma and -gamma gamma gamma coincidences recorded with the early implementation of the GAMMASPHERE array and the MICROBALL charged-particle detection system were used to largely extend the level scheme of the T-tau=1 nucleus Mo-86 to a possible spin of I=24h at 13 MeV excitation energy. The excitation scheme is compared to neighboring nuclei. There is evidence for enhanced shell-model influence in the 4 quasiparticle region (I=12-16h). The observed (pi=+,alpha=0) sequence at spin I greater than or equal to 16 h appears to be associated with a triaxial collective rotational band. This interpretation is supported by calculations within the configuration-dependent shell-correction approach with the cranked Nilsson potential.
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22.
  • Svensson, C. E., et al. (författare)
  • Lifetimes of superdeformed rotational states in 36Ar
  • 2001
  • Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 63:6, s. 613011-613015
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes have been measured in a superdeformed rotational band recently identified in the N = Z nucleus 36Ar. A large low-spin quadrupole deformation (β2=0.46±0.03) is confirmed and a decrease in the collectivity is observed as the high-spin band termination at Iπ=16+ is approached. Detailed comparisons of the experimental B(E2) values with the results of cranked Nilsson-Strutinsky and large-scale (s1/2d3/2)-pf spherical shell model calculations indicate the need for a more refined treatment of transition matrix elements close to termination in the former, and the inclusion of the complete sd-pf model space in the latter description of this highly-collective rotational band.
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23.
  • Svensson, C. E., et al. (författare)
  • Lifetimes of superdeformed rotational states in [Formula Presented]
  • 2001
  • Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 63:6, s. 5-5
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes have been measured in a superdeformed rotational band recently identified in the [Formula Presented] nucleus [Formula Presented] A large low-spin quadrupole deformation [Formula Presented] is confirmed and a decrease in the collectivity is observed as the high-spin band termination at [Formula Presented] is approached. Detailed comparisons of the experimental [Formula Presented] values with the results of cranked Nilsson-Strutinsky and large-scale [Formula Presented] spherical shell model calculations indicate the need for a more refined treatment of transition matrix elements close to termination in the former, and the inclusion of the complete [Formula Presented] model space in the latter description of this highly-collective rotational band.
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24.
  • Svensson, C. E., et al. (författare)
  • Observation and Quadrupole Moment Measurement of the First Superdeformed Band in the A~60 Mass Region
  • 1997
  • Ingår i: Physical Review Letters. - 1079-7114. ; 79:7, s. 1233-1236
  • Tidskriftsartikel (refereegranskat)abstract
    • A high-spin rotational cascade of six gamma rays has been observed in Zn-62. The quadrupole moment of 2.7(-0.5)(+0.7) e b measured for this band corresponds to a deformation beta(2) = 0.45(-0.07)(+0.10). The properties of this band are in excellent agreement with calculations that predict high-spin superdeformed bands in Zn-62 with deformations beta(2) = 0.41-0.49. These results establish a new region of superdeformation for nuclei with neutron and proton numbers N, Z approximate to 30-32.
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25.
  • Torres, D. A., et al. (författare)
  • Deformations and Magnetic Rotations in the 60Ni Nucleus
  • 2008
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 78:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Data from three experiments using the heavy-ion fusion evaporation-reaction Ar-36+Si-28 have been combined to study high-spin states in the residual nucleus Ni-60, which is populated via the evaporation of four protons from the compound nucleus Ge-64. The GAMMASPHERE array was used for all the experiments in conjunction with a 4 pi charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of. rays in coincidence with the evaporated particles. An extended Ni-60 level scheme is presented, comprising more than 270 gamma-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of gamma rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations.
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