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Träfflista för sökning "WFRF:(MACCHIAVELLI AO) "

Sökning: WFRF:(MACCHIAVELLI AO)

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1.
  • Evans, AO, et al. (författare)
  • High-spin structure beyond band termination in Er-157
  • 2004
  • Ingår i: Physical Review Letters. - 1079-7114. ; 92:25
  • Tidskriftsartikel (refereegranskat)abstract
    • The angular-momentum induced transition from a deformed state of collective rotation to a noncollective configuration has been studied. In Er-157 this transition manifests itself as favored band termination near I=45 (h) over bar. The feeding of these band terminating states has been investigated for the first time using the Gammasphere spectrometer. Many weakly populated states lying at high excitation energy that decay into these special states have been discovered. Cranked Nilsson-Strutinsky calculations suggest that these states arise from weakly collective "core-breaking" configurations.
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2.
  • Evans, AO, et al. (författare)
  • High-spin structure in Er-157 up to and above band termination
  • 2006
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 73:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The high-spin structure of Er-157 has been greatly expanded using the Gammasphere spectrometer to investigate the Cd-114(Ca-48,5n) reaction at 215 MeV. Many new transitions have been placed in a greatly augmented level scheme up to spin 40h with many collective rotational sequences established. With increasing angular momentum, this nucleus undergoes a Coriolis-induced shape transition from a deformed state of collective rotation to a noncollective configuration. This transition manifests itself as favored band termination near I=45h in three rotational structures. Many weakly populated states lying at high excitation energy that decay into the terminating states have been discovered. Cranked-Nilsson-Strutinsky calculations suggest that the levels that feed the terminating states arise from weakly collective configurations that break the Z=64 semimagic core.
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3.
  • Evans, AO, et al. (författare)
  • Magnetic properties of smooth terminating dipole bands in Te-110,Te-112
  • 2006
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 636:1, s. 25-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Three strongly coupled sequences have been established in Te-110,Te-112 up to high spins. They are interpreted in terms of deformed structures built on proton 1-particle-1-hole excitations that reach termination at I similar to 40h. This is the first observation of smooth terminating dipole structures in this mass region. Lifetime measurements have allowed the extraction of experimental B(M 1; 1 -> I - 1) and B(E2; I -> I - 2) reduced transition rates for one of the dipole bands in Te-110. The results support the deformed interpretation. (c) 2006 Elsevier B.V. All rights reserved.
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4.
  • ASZTALOS, SJ, et al. (författare)
  • CONFIRMATION OF THE SUPERDEFORMED BAND IN PB-192
  • 1995
  • Ingår i: Zeitschrift für Physik A Hadrons and Nuclei. - 0939-7922 .- 1431-5831. ; 352:3, s. 239-240
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Pb-192 were populated via the reaction Yb-173(Mg-24,5n) at a beam energy of 140 MeV, and the resulting gamma-rays were deteced using GAMMA-SPHERE. A previously observed superdeformed band in Pb-192 has been confirmed.
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5.
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6.
  • BERNSTEIN, LA, et al. (författare)
  • ONSET OF COLLECTIVITY IN NEUTRON-DEFICIENT PO-196,PO-198
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 52:2, s. 621-627
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied via in-beam gamma-ray spectroscopy Po-196 and Po-198, which are the first neutron-deficient Po isotopes to exhibit a collective low-lying structure. The ratios of yrast state energies and the E2 branching ratios of transitions from non-yrast to yrast states are indicative of a low-lying vibrational structure. The onset of collective motion in these isotopes can be attributed to the opening of the neutron i(13/2) orbital at N approximate to 112 and the resulting large overlap between the two valence protons in the h(9/2) orbital and the valence neutrons in the i(13/2) orbital.
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7.
  • BERNSTEIN, LA, et al. (författare)
  • SUPERDEFORMATION IN ER-154
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 52:3, s. R1171-R1174
  • Tidskriftsartikel (refereegranskat)abstract
    • A superdeformed (SD) band consisting of 13 gamma-ray transitions has been observed in Er-154, an isotone of Dy-152(66). The experiment was performed using the Sn-118(Ar-40,4n) reaction at E(Ar-40)=185 MeV and the early implementation of GAMMASPHERE. This is an observation of a SD band in the A approximate to 150 region with a proton number greater than 66. The J((2)) moment of inertia of the band is constant above ($) over bar h omega=0.45 MeV and shows a sharp rise below this value suggesting a paired band crossing. These results suggest that total Routhian surface calculations fail to accurately predict the deformation of the band.
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8.
  • Cederwall, Bo, et al. (författare)
  • MEASUREMENT OF ULTRA-FAST GAMMA-RAY TRANSITIONS FROM HEAVY-ION COMPOUND NUCLEUS REACTIONS
  • 1995
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 354:2-3, s. 591-594
  • Tidskriftsartikel (refereegranskat)abstract
    • A method for correcting target-thickness-induced Doppler broadening in gamma-ray spectra from weakly populated, very short-lived (femtosecond) states is presented. The method is illustrated by an analysis of superdeformed transitions in Dy-152,Dy-153 for which the validity of the procedure could be verified consistently from previous lifetime measurements in Dy-152. Furthermore, estimates of the superdeformed lifetimes, previously not measured in Dy-153, are obtained.
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9.
  • Cederwall, Bo, et al. (författare)
  • NEW FEATURES OF SUPERDEFORMED BANDS IN HG-194
  • 1994
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 72:20, s. 3150-3153
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new features of superdeformed (SD) bands in the A almost-equal-to 190 region emerge from a study of Hg-194 with the Gammasphere detector array. A decrease of the dynamic moment of inertia is observed for rotational frequencies HBARomega greater-than-or-equal-to 0.4 MeV, confirming long standing expectations based on mean field calculations with pairing. Evidence for a small staggering in the SD transition energies is also observed, suggesting the presence of terms with fourfold symmetry in the SD Hamiltonian.
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10.
  • Cederwall, Bo, et al. (författare)
  • NEW OBLATE BAND IN HG-196 WITH QUENCHED M1 STRENGTH
  • 1993
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 47:6, s. R2443-R2446
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the nucleUs Hg-196 were populated in the reaction (Os(Be,5n))-Os-192 at a beam energy of 65 MeV. A regular rotational-like DELTAI = 1 band has been observed up to an excitation energy of E* almost-equal-to 8.7 MeV and spin I almost-equal-to 30hBAR. This is the second observation of a band of this character in a mercury isotope. The experimental results are compared with mean field calculations and semiclassical estimates based on the Donau-Frauendorf formalism. The mercury bands show significantly lower B(M1)/B(E2) branching ratios as compared with similar bands in light lead nuclei. This difference may be more readily explained by a difference in single-particle structure rather than by large differences in deformation between the lead and mercury configurations.
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11.
  • Cederwall, Bo, et al. (författare)
  • PROPERTIES OF SUPERDEFORMED BANDS IN DY-153
  • 1995
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 346:3-4, s. 244-250
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new superdeformed (SD) bands in Dy-153, in addition to the three previously observed, have been studied with the GAMMASPHERE detector array. Assignments to single-neutron orbits in the SD potential are made based on the band properties. Evidence for a band interaction at very high spins, possibly involving the first N = 7 proton intruder orbital, is observed in the strongest populated SD band. Furthermore, evidence far a Delta I = 2 staggering is also found in this SD band.
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12.
  • Chiara, CJ, et al. (författare)
  • Transition Quadrupole Moments in the Superdeformed Band of 40Ca
  • 2003
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The transition quadrupole moments Q(t) for the superdeformed band in Ca-40 have been determined through thin-target Doppler-shift attenuation analyses. A best-fit value of Q(t)=1.30+/-0.05 e b is obtained when a single value is assumed for the entire band. Fitting separate quadrupole moments for in-band transitions decaying from the high-spin states and the presumably admixed low-spin states results in Q(t)(high)= 1.81(-0.26)(+0.41) e b and Q(t)(low)=1.18(-0.05)(+0.06) e b, respectively. Q(t) values extracted for individual transitions in a Doppler-broadened line-shape analysis also indicate smaller Q(t) values at lower spins. These results are consistent with the interpretation of this band as an eight-particle-eight-hole superdeformed band with a significant admixture of less-collective configurations at low spins.
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13.
  • CLARK, RM, et al. (författare)
  • A PAIR OF IDENTICAL SUPERDEFORMED BANDS IN ND-136
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 343:1-4, s. 59-63
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Nd-136 were populated via the Mo-100(Ar-40, 4n) reaction at beam energies of 176 and 182 MeV, and resulting gamma-rays were detected using the GAMMASPHERE spectrometer. Analysis of the data has revealed the existence of an excited superdeformed (SD) band in Nd-136. Th, yrast SD band in Nd-136 has been extended by the addition of four (possibly five) transitions at high frequency. The new band displays the remarkable property of having transition energies identical (to within +/- 1 keV) to those of the half-points of the yrast SD band of Nd-136. Possible explanations in terms of cranked Woods-Saxon single-particle calculations are discussed.
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14.
  • CLARK, RM, et al. (författare)
  • SUPERDEFORMATION IN THE BISMUTH NUCLEI
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 51:3, s. R1052-R1056
  • Tidskriftsartikel (refereegranskat)
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15.
  • CRISTANCHO, F, et al. (författare)
  • MULTIPLE SUPERDEFORMED BANDS IN SR-81
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 357:3, s. 281-286
  • Tidskriftsartikel (refereegranskat)abstract
    • Four superdeformed bands extending over five to twelve transitions have been identified in Sr-81 from a study With the Gammasphere array and the Microball charged-particle array, One of the bands shows an upbend in the dynamic moment of inertia at a rotational frequency of 1.2 MeV and all bands exhibit a nearly constant moment of inertia below that frequency.
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16.
  • DELEPLANQUE, MA, et al. (författare)
  • LOW-SPIN TERMINATION OF THE SUPERDEFORMED BAND IN ND-135
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 52:5, s. R2302-R2305
  • Tidskriftsartikel (refereegranskat)abstract
    • The decay of the superdeformed (SD) band in Nd-135 was studied with the early implementation of gamma-sphere. The results suggest that the SD band ''terminates'' at spin 25/2. This termination is explained by a change of the SD minimum toward a triaxial lower deformation. Ultimate cranker calculations with the i(13/2) orbital occupied relate this change to a shift of a proton and neutron pair out of deformation-driving Nilsson orbitals. This is a completely new and unexpected mechanism for the decay of SD bands.
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17.
  • du Rietz, Rickard, et al. (författare)
  • Investigation of High-spin States in 53Fe
  • 2005
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 72:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The fusion-evaporation reactions Si-28(S-32,1 alpha 2p1n)Fe-53 at 125 MeV and Mg-24(S-32,2p1n)Fe-53 at a 95-MeV beam energy were used to investigate excited states in Fe-53. The combination of the Gammasphere Ge detector array and ancillary devices led to the construction of an extensive level scheme comprising some 90 transitions connecting 40 states. The lifetime of the yrast 25/2(-) state and upper limits for the lifetimes of a number of additional states were determined using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The experimental results are compared to large-scale shell-model calculations using different sets of two-body matrix elements. In particular, predictions on electromagnetic decay properties such as lifetimes, branching ratios, and mixing ratios are studied in detail.
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18.
  • Ekman, Jörgen, et al. (författare)
  • Core Excited States in the A=51 Mirror Nuclei
  • 2004
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Three previously unknown high-energy gamma-ray transitions between 4.2 and 5.4 MeV were identified in the T-z=-1/2 nucleus Fe-51 following the fusion-evaporation reaction S-32(Si-28, 2alpha1n)Fe-51. These transitions represent decays of core excited states. The gamma rays were detected in the Ge detector array Gammasphere combined with the neutron detector system Neutron Shell and the charged-particle array Microball. The three transitions are related to the mirror transitions in the T-z= + 1 /2 nucleus Mn-51, and the resulting mirror-energy difference diagram is discussed with predictions from large-scale shell-model calculations.
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19.
  • Ekman, Jörgen, et al. (författare)
  • Evidence for a 1g9/2 Rotational Band in 51Mn
  • 2002
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 66:5, s. 513011-513015
  • Tidskriftsartikel (refereegranskat)abstract
    • A terminating rotational band has been identified in Mn-51 following the Si-28(S-32,2alpha1p)Mn-51 fusion-evaporation reaction at 130 MeV beam energy. Spins and tentative positive parities of the band members are assigned based on angular distribution and correlation measurements of transitions, which connect the rotational structure with previously known yrast states. Configuration-dependent cranked Nilsson-Strutinsky calculations suggest a configuration of the band, which comprises one particle in the 1g(9/2) intruder orbit.
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20.
  • Ekman, Jörgen, et al. (författare)
  • Gamma-ray Spectroscopy of Core-excited States in 51Mn
  • 2004
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The level scheme of Mn-51 has been investigated using the Si-28(S-32 2alpha1p)Mn-51 fusion-evaporation reaction at 125 MeV beam energy. The gamma rays were detected in the Ge-detector array Gammasphere, which was coupled to the 4pi-charged-particle detector Microball and the Neutron Shell for the coincident detection of evaporated particles. Over 100 new gamma-ray transitions connecting some 50 excited states have been identified. Most of the states are built on particle-hole excitations across the shell gaps at particle number N=Z=28. The rich experimental data allows for a 'comprehensive comparison of core-excited states with results from large-scale shell-model calculations, which are known to provide excellent predictions for the lower-lying yrast and near-yrast levels in 1f(7/2) nuclei.
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21.
  • FALLON, P, et al. (författare)
  • PROTON AND NEUTRON EXCITATIONS IN SUPERDEFORMED TB-150
  • 1995
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 52:1, s. 93-98
  • Tidskriftsartikel (refereegranskat)abstract
    • Two new superdeformed (SD) bands have been observed in Tb-150 using the reaction P-31 + Sn-124 and the GAMMASPHERE detector array. These new bands are interpreted as being excited SD configurations involving a proton and a neutron particle-hole excitation, respectively. The configurations are discussed in terms of the occupancy of high-N intruder orbitals. These data are used to provide information on (i) the contribution to the dynamic moments of inertia due to the occupation of specific orbitals, (ii) the deformation driving effects of the particle-hole states, and (iii) the consequences of these effects on pairing and band crossings.
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22.
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24.
  • Gorgen, A, et al. (författare)
  • Quadrupole moments of wobbling excitations in Lu-163
  • 2004
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 69:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of states in the triaxial strongly deformed bands of Lu-163 have been measured with the Gammasphere spectrometer using the Doppler-shift attenuation method. The bands have been interpreted as wobbling-phonon excitations from the characteristic electromagnetic properties of the transitions connecting the bands. Quadrupole moments are extracted for the zero-phonon yrast band and, for the first time, for the one-phonon wobbling band. The very similar results found for the two bands suggest a similar intrinsic structure and support the wobbling interpretation. While the in-band quadrupole moments for the bands show a decreasing trend towards higher spin, the ratio of the interband to the in-band transition strengths remains constant. Both features can be understood by a small increase in triaxiality towards higher spin. Such a change in triaxiality is also found in cranking calculations, to which the experimental results are compared.
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25.
  • HUGHES, JR, et al. (författare)
  • EXCITATIONS IN DOUBLY-MAGIC SUPERDEFORMED PB-194
  • 1994
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 50:3, s. R1265-R1269
  • Tidskriftsartikel (refereegranskat)abstract
    • A new superdeformed band with an intensity similar to 5% relative to the yrast superdeformed band has been observed in Pb-194. Evidence for a second new band corresponding to the signature partner is also presented. These bands were observed with GAMMASPHERE early implementation via the Yb-174(Mg-25, 5n) reaction at a beam energy of 130 MeV. The rotational characteristics of the new bands suggest an interpretation involving particle-hole excitations in the doubly-magic Pb-194 superdeformed core. The results are compared to neighboring nuclei and recent theoretical calculations, and possible configurations are suggested.
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26.
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27.
  • JIN, HQ, et al. (författare)
  • IDENTIFICATION AND QUADRUPOLE-MOMENT MEASUREMENT OF A SUPERDEFORMED BAND IN ZR-84
  • 1995
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 75:8, s. 1471-1474
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Zr-84 were studied using the early implementation phase of the Gammasphere array and the ''Microball'' charged-particle detector system. A cascade of nine gamma rays with a dynamic moment of inertia which is characteristic of superdeformed rotational bands in the A = 80 region has been identified and assigned to Zr-84. The measured transition quadrupole moment of the band corresponds to a prolate quadrupole deformation of beta(2) = 0.53 and confirms the superdeformed nature of this band. This is the first direct experimental confirmation of the existence of the predicted superdeformed shell gap at N similar or equal to 44 particle number.
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28.
  • Johansson, Emma, et al. (författare)
  • Gamma-ray Spectroscopy of the Doubly Magic Nucleus 56Ni
  • 2006
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 27:2, s. 157-165
  • Tidskriftsartikel (refereegranskat)abstract
    • The doubly magic N = Z nucleus Ni-56 has been investigated with two fusion-evaporation reactions; Ca-40(Si-28, 3 alpha)Ni-56 at a beam energy of 122MeV and Si-28(S-32, 2p2n)Ni-56 at 130MeV. To detect gamma-rays in coincidence with evaporated particles the Ge-detector array Gammasphere was used in conjunction with the charged-particle detector system, Microball and a 1 pi neutron detector array. Results include a significantly extended level scheme of Ni-56, which is compared to large-scale shell model calculations in the fp shell. The experimental and theoretical results agree to a large extent, with one notable exception; the theoretical model fails to predict the proper sequence of the yrast and yrare 8(+) states.
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29.
  • Kelsall, NS, et al. (författare)
  • High-spin structure of N similar or equal to Z nuclei around the A=72 region
  • 2004
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 20:1, s. 131-132
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states have been studied in Kr-72 and Br-72 using the Ca-40 + Ca-40 and Ar-36 + Ca-40 reactions at 164 and 145 MeV, respectively. The properties and configurations of the high-spin bands observed have been interpreted using impaired cranked Nilssou-Strutinsky (CNS), and for Kr-72, paired cranked relativistic Hartree-Bogoliubov (CRHB) calculations. In Kr-72 a new band has been identified that has the properties expected for the doubly aligned S-band configuration. In Br-72 the previously known bands have been extended to higher spin. This has lead to a re-interpretation of the configurations.
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30.
  • LAFOSSE, DR, et al. (författare)
  • CHARACTERIZATION OF THE FIRST SUPERDEFORMED BAND IN THE A-APPROXIMATE-TO-80 REGION
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 354:1-2, s. 34-40
  • Tidskriftsartikel (refereegranskat)abstract
    • The recently discovered superdeformed band in one of the strontium isotopes has been identified as belonging to Sr-83 from a study with the Gammasphere array and the Microball charged-particle detector system. From its decay pattern, a spin of (81 +/- 2)/2 ($) over bar h is deduced for the highest level of this band. Evidence for very fast transition rates and agreement of the characteristics of this band with the theoretical predictions establish the yrast superdeformed nature of this band in Sr-83.
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31.
  • LAFOSSE, DR, et al. (författare)
  • EVIDENCE FOR HYPERDEFORMATION IN GD-147
  • 1995
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 74:26, s. 5186-5189
  • Tidskriftsartikel (refereegranskat)
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32.
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33.
  • NISIUS, D, et al. (författare)
  • IDENTICAL SUPERDEFORMED BAND IN DY-151 - FURTHER EVIDENCE FOR THE PSEUDOSPIN COUPLING SCHEME
  • 1995
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 346:1-2, s. 15-20
  • Tidskriftsartikel (refereegranskat)abstract
    • One of the four new excited superdeformed bands found in Dy-151 is characterized by transition energies that lie midway between the gamma-ray energies of the yrast superdeformed band in Dy-152. This result adds significant new information on the issue of ''identical'' bands, as it confirms predictions based on the strong coupling model and the pseudospin coupling scheme.
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34.
  • O'Leary, CD, et al. (författare)
  • Evidence for isovector neutron-proton pairing from high-spin states in N=Z Rb-74
  • 2003
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:2: 021301
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the odd-odd N=Z nucleus Rb-74(37)37 were studied using the Ca-40(Ca-40,alphanp) reaction. A previously observed odd-spin T=0 band has been extended to I-pi=(31(+)) and an even-spin T=0 band has been observed for the first time to I-pi=(22(+)); both have a pi(g(9/2))circle timesnu(g(9/2)) structure. A strongly coupled low-spin T=0,K=3 band has been interpreted as being based upon a pi[312]3/2 circle timesnu[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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35.
  • OLIVEIRA, JRB, et al. (författare)
  • HIGH-K BANDS IN THE YB-166 REGION
  • 1994
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 50:3, s. 1360-1369
  • Tidskriftsartikel (refereegranskat)abstract
    • High-K bands have been observed in the Yb-166,Yb-167,Yb-168 isotopes following the Sn-124(Ca-48,xn gamma) reaction. The nu h(11/2) bend in Yb-167 has been extended to higher spins. The high-K bands in the even-even isotopes were observed for the first time and show very high B(M1)/B(E2) ratios. Configuration assignments for the new bands are proposed. The results are interpreted within the tilted cranking model.
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36.
  • Pavan, J, et al. (författare)
  • Lifetime measurements and terminating structures in Nb-87
  • 2003
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:3: 034316
  • Tidskriftsartikel (refereegranskat)abstract
    • Two experiments have been performed using the Ni-58(S-32,3p) reaction at 135 MeV with Gammasphere and the Microball to study the high-spin structure of the transitional nucleus Nb-87. The first experiment using a thin target provided a considerable extension and refinement of the level scheme, as well as firm spin assignments from directional correlation of oriented nuclei. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of beta(2)similar to0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transitions between some pairs of bands. The experimental results were compared with calculations performed within the cranked Nilsson-Strutinsky approach. The calculations generally reproduce the irregularities in the structure of the yrast lines and plunging transition quadrupole moments Q(t) within the bands explaining them as reflections of configuration changes and an approach of band termination, respectively.
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37.
  • Robinson, SD, et al. (författare)
  • High-spin structures and band termination effects in Cd-104
  • 2002
  • Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899. ; 28:6, s. 1415-1431
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in the neutron-deficient isotope Cd-104 were populated using the Cr-50(Ni-58,4p)Cd-104 reaction at a beam energy of 250 MeV The level scheme has been extended using triple gamma-ray coincidences to a spin of 29h and an excitation energy of 18.2 MeV. Several collective structures involving the excitation of h(11/2) neutrons have been observed to spins approaching 30h. The high-spin structure has been compared to the results of cranked Nilsson-Strutinsky calculations.
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38.
  • Rudolph, Dirk, et al. (författare)
  • 58Ni: An Unpaired Band Crossing at New Heights of Angular Momentum for Rotating Nuclei
  • 2006
  • Ingår i: Physical Review Letters. - 1079-7114. ; 96:9
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Ni-58 have been investigated by means of the fusion-evaporation reaction Si-28(S-32,2p)Ni-58 at 130 MeV beam energy. Discrete-energy levels are observed in Ni-58 at record-breaking 42 MeV excitation energy and angular momenta in excess of 30h. The states form regular rotational bands with unprecedented high rotational frequencies. A comparison with configuration dependent cranked Nilsson-Strutinsky calculations reveals an exceptional two-band crossing scenario, the interaction strength of which is strongly shape dependent.
  •  
39.
  • Singh, AK, et al. (författare)
  • Evidence for noncollective oblate structures at high spin in Cs-123
  • 2004
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:3
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Cs-123 were populated in the Ni-64(Ni-64,p4n) reaction at a beam energy of 265 MeV. Gamma-ray coincidences were measured using the Gammasphere spectrometer. Two additional bands have been placed in the level scheme and the four previously known bands have been extended to higher spin. At the highest spins, two of the bands show irregular level sequences. These structures of noncollective excitations, which compete with collective rotation, are interpreted as band-terminating states. The results are compared to cranked Nilsson-Strutinsky calculations, and configuration assignments to the bands and to the terminating states are discussed.
  •  
40.
  • Valiente-Dobon, JJ, et al. (författare)
  • Evidence for nontermination of rotational bands in Kr-74
  • 2005
  • Ingår i: Physical Review Letters. - 1079-7114. ; 95:23
  • Tidskriftsartikel (refereegranskat)abstract
    • Three rotational bands in Kr-74 were studied up to (in one case one transition short of) the maximum spin I-max of their respective single-particle configurations. Their lifetimes have been determined using the Doppler-shift attenuation method. The deduced transition quadrupole moments reveal a modest decrease, but far from a complete loss of collectivity at the maximum spin I-max. This feature, together with the results of mean field calculations, indicates that the observed bands do not terminate at I=I-max.
  •  
41.
  • Valiente-Dobon, JJ, et al. (författare)
  • High-spin rotational structures in Kr-76
  • 2005
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:3
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Kr-76(36)40 have been populated in the Ca-40(Ca-40,4p)Kr-76 fusion-evaporation reaction at abeam energy of 165 MeV and studied using the Gammasphere and Microball multidetector arrays. The ground-state band and two signature-split negative parity bands of Kr-76 have been extended to similar to 30 (h) over bar. Lifetime measurements. using the Doppler-shift attenuation method show that the transition quadrupole moment of these three bands decrease as they approach their maximum-spin states. Two signatures of a new rotational structure with remarkably rigid rotational behavior have been identified. The high-spin properties of these rotational bands are analyzed within the framework of configuration-dependent cranked Nilsson-Strutinsky calculations.
  •  
42.
  • Valiente-Dobon, JJ, et al. (författare)
  • Lifetimes of high-spin states in Kr-76
  • 2005
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 36:4, s. 1339-1342
  • Tidskriftsartikel (refereegranskat)abstract
    • High-spin states in Kr-76(36)40 have been populated in the Ca-40 (Ca-40,4p) Kr-76 fusion-evaporation reaction at a beam energy of 165 MeV, and studied using the GAMMASPHERE and MICROBALL multi-detector arrays. The ground-state band and two signature-split negative-parity bands of Kr-76 have been extended to similar to 30h. Lifetime measurements using the Doppler-shift attenuation method indicate that the transition quadrupole moment of these three bands decrease as they approach their maximum-spin states.
  •  
43.
  • VO, DT, et al. (författare)
  • SUPERDEFORMATION IN AU-191
  • 1993
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 71:3, s. 340-343
  • Tidskriftsartikel (refereegranskat)abstract
    • A superdeformed band has been observed for the first time in an Au isotope. The reaction used was B-11 + W-186, demonstrating that very light ions can be used to populate superdeformed (SD) bands at high angular momentum. The band is assigned to 191Au. The gamma-ray energies are at the quarter-point energies of the 192Hg SD band, indicating that it is ''identical'' to that of 192Hg.
  •  
44.
  • Yu, CH, et al. (författare)
  • Rotational Bands with Terminating Properties in 59Ni
  • 2002
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 65:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Highly-deformed rotational bands were established in Ni-59 using the Ca-40(Si-29,2p2alpha)Ni-59 reaction. Lifetime measurements indicate that transition quadrupole moments of two of these bands decrease as they smoothly approach their maximum-spin states. The configurations of these bands as well as their band-terminating features are discussed based on configuration-dependent cranked Nilsson-Strutinsky calculations. These calculations indicate that, unlike similar bands observed previously in the region, the two bands in Ni-59 maintain significant collectivity at their I=I-max states.
  •  
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