Structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Xe</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>126</mml:mn><mml:mo>,</mml:mo><mml:mn>128</mml:mn></mml:mrow></mml:mmultiscripts></mml:math> studied in Coulomb excitation measurements
S. Kisyov, C. Y. Wu, J. Henderson, A. Gade, Kazunari Kaneko, Yang Sun, Noritaka Shimizu, T. Mizusaki, D. Rhodes, S. Biswas, A. Chester, M. Devlin, P. Farris, A. M. Hill, J. Li, E. Rubino, D. Weißhaar
Abstract
The electromagnetic properties of $^{126,128}\mathrm{Xe}$ were studied in subbarrier Coulomb excitation measurements performed at the National Superconducting Cyclotron Laboratory Re-accelerator facility, ReA3, at Michigan State University (MSU). $^{126}\mathrm{Xe}$ and $^{128}\mathrm{Xe}$ nuclei were accelerated to 3.74 and 3.81 MeV/nucleon, respectively, and were impinged on $^{196}\mathrm{Pt}$ and $^{208}\mathrm{Pb}$ targets. The $\ensuremath{\gamma}$ rays deexciting the populated low-lying states were detected in coincidence with the scattered nuclei using the JANUS setup. Transition and diagonal matrix elements for low-lying states and transitions in $^{126,128}\mathrm{Xe}$ were extracted from the experimental data using the gosia and gosia2 codes. The experimental results were compared with the theoretical calculations by the microscopic shell model and the Davydov-Filippov $\ensuremath{\gamma}$-rigid rotor model. The calculated results from the newly established shell model (called the PMMU model), which is based on the advanced Hartree-Fock Bogoliubov plus generator coordinate method (HFB $+$ gcm) for a large model space, agree well with the measurements in both nuclei, except for the second ${2}^{+}$ state. Interpretation for the experimentally determined nearly vanishing electric-quadrupole moment of this state remains a challenge for theory.