| 1. |
- Henning, G., et al.
(författare)
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Fission Barrier of Superheavy Nuclei and Persistence of Shell Effects at High Spin: Cases of No-254 and Th-220
- 2014
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 113:26
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first measurement of the fission barrier height in a heavy shell-stabilized nucleus. The fission barrier height of No-254 is measured to be B-f = 6.0 +/- 0.5 MeV at spin 15 (h) over bar and, by extrapolation, B-f = 6.6 +/- 0.9 MeV at spin 0 (h) over bar. This information is deduced from the measured distribution of entry points in the excitation energy versus spin plane. The same measurement is performed for Th-220 and only a lower limit of the fission barrier height can be determined: B-f (I) > 8 MeV. Comparisons with theoretical fission barriers test theories that predict properties of superheavy elements.
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| 2. |
- Albers, M., et al.
(författare)
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Single-particle and collective excitations in Ni-63
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:5
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Tidskriftsartikel (refereegranskat)abstract
- A study of excited states in Ni-63 up to an excitation energy of 28 MeV and a probable spin of 57/2 was carried out with the Mg-26(Ca-48,2 alpha 3n gamma)Ni-63 reaction at beam energies between 275 and 320 MeV. Three collective bands, built upon states of single-particle character, were identified. For two of the three bands, the transition quadrupole moments were extracted, herewith quantifying the deformation at high spin. The results have been compared with shell-model and cranked Nilsson-Strutinsky calculations. Despite the Z = 28 shell closure and the approach to the purported N = 40 subshell, the Ni-63 isotope is able to sustain collective excitations at moderate and high spin.
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| 3. |
- Nag, Somnath, et al.
(författare)
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Collective and noncollective excitations in Te-122
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:4
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Te-122 were populated in the reaction Se-82(Ca-48, alpha 4n) Te-122 at a beam energy of 200 MeV and gamma-ray coincidences weremeasured with the Gammasphere spectrometer. The previously known level scheme was extended to considerably higher spin. Maximally aligned states and several high-energy transitions feeding into some of these levels were observed. In addition, seven collective high-spin bands were discovered for the first time in this nucleus. The experimental results are compared with cranked Nilsson-Strutinsky model calculations and possible configuration assignments to the new high-spin structures are discussed.
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| 4. |
- Nag, Somnath, et al.
(författare)
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Collective and noncollective states in (120)Te
- 2012
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:1
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in (120)Te were populated in the reaction (80)Se((48)Ca, alpha 4n)(120)Te at a beam energy of 207 MeV and gamma-ray coincidences were measured using the Gammasphere spectrometer. The previously known level scheme is extended to higher spin and new interband transitions and side-feeding branches are established. Five highly deformed rotational bands, extending up to almost I = 50, are observed for the first time. The bands are compared with similar structures found recently in neighboring nuclei. The experimental results are interpreted within the framework of the cranked Nilsson-Strutinsky model. Configuration assignments to several terminating states and to the high-spin bands are discussed.
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| 5. |
- Nag, Somnath, et al.
(författare)
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Revised level structure of Te-120
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:3
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Tidskriftsartikel (refereegranskat)abstract
- The level scheme of the nucleus Te-120, populated in the reaction Se-80(Ca-48, alpha 4n), was reinvestigated using gamma-ray coincidence data measured with the Gammasphere spectrometer. Previously, five high-spin rotational bands were discovered in this nucleus. The present reinvestigation revealed that the decay of band b1 is more complex than suggested in the earlier work and that it cannot be uniquely determined. Furthermore, a number of new transitions are added to the level scheme. The implications for the spin assignments and excitation energies of the five bands and for comparisons with cranked Nilsson-Strutinsky calculations are discussed.
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| 6. |
- Singh, Purnima, et al.
(författare)
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Core excitations beyond maximally aligned configurations in I-123
- 2012
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:3
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in I-123 have been populated in the Se-80(Ca-48, p4n) I-123 reaction at 207 MeV and gamma-ray coincidence events have been recorded with the Gammasphere spectrometer. The level scheme of I-123 has been extended up to spin I = 63/2. The nucleus undergoes a shape transition from moderately deformed states with collective rotation at low spins to noncollective oblate configurations at higher spins. Maximally aligned terminating states involving all nine particles outside the Sn-114 core and states with one particle antialigned are identified. A large number of weak transitions feed the terminating states. Cranked Nilsson-Strutinsky calculations have been performed to determine possible configurations for the observed energy levels.
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| 7. |
- Singh, Purnima, et al.
(författare)
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High-spin rotational bands in I-123
- 2012
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 86:6
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in I-123 were populated in the reaction Se-80(Ca-48,p4n)I-123 at a beam energy of 207 MeV and gamma-ray coincidence events were measured using the Gammasphere spectrometer. Three weakly populated, high-spin rotational bands have been discovered with characteristics similar to those of the long collective bands recently observed in other nuclei of this mass region. Configuration assignments are proposed based on calculations within the framework of the cranked Nilsson-Strutinsky approach. DOI: 10.1103/PhysRevC.86.067305
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| 8. |
- Singh, Purnima, et al.
(författare)
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Highly deformed high-spin band in I-125
- 2011
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 84:2
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in I-125 have been investigated using the reaction Se-82(Ca-48, p4n) at a beam energy of 200 MeV and gamma-ray coincidence events were detected using the Gammasphere spectrometer. A deformed rotational band, extending up to I-pi = 95/2(-), was observed for the first time in a heavier odd-A iodine nucleus. The characteristics of the band are very similar to those of the highly deformed bands observed recently in neighboring nuclei and it is essentially identical to one of the previously known bands in Xe-126. The experimental results are compared to cranked Nilsson-Strutinsky calculations and possible configurations for the band are discussed.
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| 9. |
- Singh, Purnima, et al.
(författare)
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Noncollective aligned and antialigned states in I-125
- 2010
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 82:3
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in I-125 were populated using the reaction Se-82(Ca-48, p4n) at a beam energy of 200 MeV and gamma-ray coincidence events were acquired with the Gammasphere spectrometer. The level scheme of I-125 was extended considerably. In particular, maximally aligned states involving all eleven particles outside the Sn-114 core were observed. Comparison with cranked Nilsson-Strutinsky calculations suggests that three of these states are the final I-max states in terminating bands with all spin vectors aligned along a common axis. In two of these, one spin vector is antialigned and points in the opposite direction. In one of the states two spin vectors are antialigned. This is the first observation of a state with such a structure.
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| 10. |
- Hayes, A. B., et al.
(författare)
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Coulomb excitation of a Am-242 isomeric target: E2 and E3 strengths, rotational alignment, and collective enhancement
- 2010
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 82:4
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Tidskriftsartikel (refereegranskat)abstract
- A 98% pure Am-242m ( K = 5(-), t(1/2) = 141 years) isomeric target was Coulomb excited with a 170.5-MeV Ar-40 beam. The selectivity of Coulomb excitation, coupled with the sensitivity of Gammasphere plus CHICO, was sufficient to identify 46 new states up to spin 18h in at least four rotational bands; 11 of these new states lie in the isomer band, 13 in a previously unknown yrast K-pi = 6(-) rotational band, and 13 in a band tentatively identified as the predicted yrast K-pi = 5(+) band. The rotational bands based on the K-pi = 5- isomer and the 6(-) bandhead were populated by Coulomb excitation with unexpectedly equal cross sections. The gamma-ray yields are reproduced by Coulomb excitation calculations using a two-particle plus rotor model (PRM), implying nearly complete Delta K = 1 mixing of the two almost-degenerate rotational bands, but recovering the Alaga rule for the unperturbed states. The degeneracy of the 5(-) and 6(-) bands allows for precise determination of the mixing interaction strength V, which approaches the strong-mixing limit; this agrees with the 50% attenuation of the Coriolis matrix element assumed in the model calculations. The fractional admixture of the I-K(pi) = 6(6)(-) state in the nominal 6(5)(-) isomer band state is measured within the PRM as 45.6(-1.1)(+0.3)%. The E2 and M1 strengths coupling the 5(-) and 6(-) bands are enhanced significantly by the mixing, while E1 and E2 couplings to other low-K bands are not measurably enhanced. The yields of the 5(+) band are reproduced by an E3 strength of approximate to 15 W.u., competitive with the interband E2 strength. Alignments of the identified two-particle Nilsson states in Am-242 are compared with the single-particle alignments in Am-241.
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