Early signal of emerging nuclear collectivity in neutron-rich $^{129}$Sb

T. J. Gray; J. M. Allmond; A. E. Stuchbery; C. -H. Yu; C. Baktash; A. Gargano; A. Galindo-Uribarri; D. C. Radford; J. C. Batchelder; J. R. Beene; C. R. Bingham; L. Coraggio; A. Covello; M. Danchev; C. J. Gross; P. A. Hausladen; N. Itaco; W. Krolas; J. F. Liang; E. Padilla-Rodal; J. Pavan; D. W. Stracener; R. L. Varner

doi:10.1103/physrevlett.124.032502

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arXiv · 1912.09612

Early signal of emerging nuclear collectivity in neutron-rich $^{129}$Sb

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Abstract

Radioactive $^{129}$Sb, which can be treated as a proton plus semi-magic $^{128}$Sn core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, $B(E2)$, for the $2^+$ $\times$ $πg_{7/2}$ multiplet members and candidate $πd_{5/2}$ state were measured. The results indicate that the total electric quadrupole strength of $^{129}$Sb is a factor of 1.39(11) larger than the $^{128}$Sn core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations performed with two different sets of nucleon-nucleon interactions suggest that this enhanced collectivity is due to constructive quadrupole coherence in the wavefunctions stemming from the proton-neutron residual interactions, where adding one nucleon to a core near a double-shell closure can have a pronounced effect. The enhanced electric quadrupole strength is an early signal of the emerging nuclear collectivity that becomes dominant away from the shell closure.

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T. J. Gray, J. M. Allmond, A. E. Stuchbery, C. -H. Yu, C. Baktash, A. Gargano, A. Galindo-Uribarri, D. C. Radford, J. C. Batchelder, J. R. Beene, C. R. Bingham, L. Coraggio, A. Covello, M. Danchev, C. J. Gross, P. A. Hausladen, N. Itaco, W. Krolas, J. F. Liang, E. Padilla-Rodal, J. Pavan, D. W. Stracener, R. L. Varner. 2019-12-20. Early signal of emerging nuclear collectivity in neutron-rich $^{129}$Sb. https://doi.org/10.1103/physrevlett.124.032502

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