Magnetic rotation and shape mixing inCe134

Abstract

High spin states of $^{134}\mathrm{Ce}$ have been studied using an array of 8 Compton suppressed clover detectors and a multiplicity filter consisting of $14\phantom{\rule{0.3em}{0ex}}\text{NaI}(\mathrm{T}1)$ detectors. Two new $\ensuremath{\Delta}I=1$ bands $B4$ and $B5$ with strong intraband magnetic dipole transitions have been established. The crossover $E2$ transitions have been observed in the $B4$ band and lifetimes of levels, both in $B4$ and $B5$ bands, have been measured using the Doppler shift attenuation method. The measured $B(M1)$ values are large for the $B4$ band, yet the measured $B(M1)∕B(E2)$ ratios are nearly constant with increasing frequency and do not support the magnetic rotation character. The $B4$ band also exhibits a small gain in alignment at a higher frequency suggesting an upbending and a band crossing. These features are sought to be explained in terms of two closely lying configurations $A:\ensuremath{\pi}{({g}_{7∕2})}^{2}\ensuremath{\bigotimes}\ensuremath{\nu}({h}_{11∕2}{d}_{3∕2})$ and $B:\ensuremath{\pi}{({h}_{11∕2})}^{2}\ensuremath{\bigotimes}\ensuremath{\nu}({h}_{11∕2}{d}_{3∕2})$, which have a small and a moderate deformation, respectively. The tilted axis cranking (TAC) calculations suggest that configuration $B$ crosses the configuration $A$ with a small alignment gain and mixing between the two may explain the observed features. The measured $B(M1)$ values deduced from the lifetimes for the $B5$ band show a decrease with increasing spin which is a characteristic feature of magnetic rotation bands. The results of the TAC calculations explain the $B5$ band very well by using the four-quasiparticle configuration $\ensuremath{\pi}({g}_{7∕2}{h}_{11∕2})\ensuremath{\bigotimes}\ensuremath{\nu}({h}_{11∕2}^{\ensuremath{-}2})$ and establish it as a magnetic rotational band.