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J. Pedersen B. B. Back S. Bjørnholm J. Borggreen G. Sletten F. Azgui H. Emling H. Grein G. Seiler-Clark W. Spreng H. J. Wollersheim P. Walker 《Zeitschrift für Physik A Hadrons and Nuclei》1985,321(4):567-575
Results of a search for high-spin isomers in W and Os nuclei withN=104–107 are presented. Targets of48Ca and48, 50Ti are bombarded with a pulsed136Xe beam, and delayed gamma-radiation is detected by an array of NaI- and Ge-detectors. Several new isomers, with spin values up to ~22h, are found in178,180W and180, 182, 183Os. Markedly different decay patterns and hindrance factors are found in the Os isotopes as compared to the expectations based on theK-selection rule valid for axially symmetric nuclei. The findings are ascribed to the onset of triaxial distortions. 相似文献
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J. Borggreen S. Bjørnholm O. Christensen A. Del Zoppo B. Herskind J. Pedersen G. Sletten F. Folkmann R. S. Simon 《Zeitschrift für Physik A Hadrons and Nuclei》1980,294(2):113-124
A NaI sum-spectrometer combined with Ge-counters has been used to characterize the members of the island of high spin isomers nearN=82. On the basis of half lives, totalγ-decay energies and discreteγ-lines, assignments of 22 isomers are given or confirmed. The isomers are localized to the region 82≦N≦86 andZ≦68, and the excitation energies vary from 3 MeV to 12.2 MeV. An empirical relation between spin and excitation energy is presented and on this basis isomeric spin values up to (33±2)? are deduced. The isomers are thought to be due to strong alignment of 2 to 8 shell-model particles in a spherical or possibly weakly oblate potential. 相似文献
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S. Bjørnholm J. Borggreen O. Echt K. Hansen J. Pedersen H. D. Rasmussen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):47-50
Measurements of the mass abundance spectra of sodium clusters containing up to 600 atoms are presented. The clusters are produced in a seeded supersonic expansion of Ar or Kr gas, and the spectra are obtained by a time-of-flight technique. The sawtooth features in the spectra are interpreted as evidence of a regular spherical shell structure with magic numbers,N 0, scaling approximately with the cube root of the number of sodium atoms. Altogether twelve shell closings are observed,N 0=2, 8, 20, 40, 58, 92, 138, 196, 260, 344, 440 and 558. There is also a pronounced odd-even staggering all the way up toN=70. The experimentally observed intensity changes for the clusters around the magic numbers are discussed in terms of the electronic free energy,F(N), calculated at finite temperature, and the second differences of the free energy Δ2 F(N)=F(N?1)?2F(N)+F(N+1). The processes behind the non-uniform abundance distributions, and the thermodynamics of finite electron systems with non-uniform level spacings are discussed on this basis. 相似文献
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J. Pedersen J. Borggreen P. Chowdhury N. Kebaïli L. Lundsberg-Nielsen K. Lützenkirchen M. B. Nielsen H. D. Rasmussen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(1):281-283
Photo-absorption cross-sections for charged sodium clusters (14 to 48 atoms) have been measured for photon energies from 2.0 eV to 3.5 eV. The spectra are dominated by surface plasma oscillations of the valence electrons exhausting 70–100% of the dipole sum rule. The mean resonance energy of ?2.75 eV is nearly independent of cluster size. A splitting of the resonance peaks is observed for non-“magic” clusters and discussed in terms of a deformation picture involving prolate and oblate shapes. 相似文献
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J. Wilson S. R. Faber P. J. Daly I. Ahmad J. Borggreen P. Chowdhury T. L. Khoo R. D. Lawson R. K. Smither J. Blomqvist 《Zeitschrift für Physik A Hadrons and Nuclei》1980,296(2):185-186
A πh 11 2/3 level spectrum and other lowlying yrast states in149Ho have been identified in reactions of 155–180 MeV32S with121Sb and122Te targets. The results agree well with shell model predictions. 相似文献
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F. Bernthal B.B. Back O. Bakander J. Borggreen J. Pedersen G. Sletten H. Beuscher D. Haenni R. Lieder 《Physics letters. [Part B]》1978,74(3):211-214
A new 710 ns isomer in 179W is found to decay directly into backbending region of the gorund-state band. The band is observed up to spin and shows no evidence for backbending at core rotational frequencies, where the effect is observed in the 179W and 180W ground-state bands. 相似文献
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High-spin states in 182Os have been populated by the (18O, 4n) reaction and studied using in-beam spectroscopy methods. Seven side bands have been established for the first time. Three of the side bands show a band crossing. The features of the bands have been interpreted in the framework of the cranking model considering the motion of independent particles in a rotating deformed potential. The band crossings of the yrast band and of these three side bands can be explained by the rotation-alignment of a pair of quasineutrons. 相似文献