Yrast bands inI117andXe116−118: Anomalous quasiparticle alignment frequencies and band termination

Abstract

The yrast bands of neutron-deficient $^{117}\mathrm{I}$ and $^{116}\mathrm{Xe}$ have been extended to I\ensuremath{\sim}34\ensuremath{\Elzxh}, and $^{117,118}\mathrm{Xe}$ to I\ensuremath{\sim}46\ensuremath{\Elzxh}, using highfold \ensuremath{\gamma}-ray coincidence data collected with the Eurogam II spectrometer. Systematic quasiparticle alignment frequencies are discussed and compared to theoretical cranked Woods-Saxon calculations. The first pair alignment is attributed to ${\mathit{h}}_{11/2}$ protons despite theoretical expectations for ${\mathit{h}}_{11/2}$ neutron alignment; the neutron alignment appears significantly delayed. At higher spins, the $^{117}\mathrm{I}$ and $^{117}\mathrm{Xe}$ isobars exhibit contrasting forms of band termination.