Single-particle and collective degrees of freedom inZr101andMo103,105

Abstract

The $g$ factors of several low-lying excited states of the neutron-rich $^{101}\mathrm{Zr}$ and $^{103,105}\mathrm{Mo}$ nuclei have been measured for the first time. The isotopes were produced by the spontaneous fission of a $^{252}\mathrm{Cf}$ source, which was sandwiched between two magnetized iron foils and placed at the center of the Gammasphere spectrometer. The $g$ factors of excited states of fission fragments were inferred from Larmor precessions deduced from the measurement of time-integrated perturbed angular correlation functions. The magnitude and sign of the quantity $({g}_{K}\ensuremath{-}{g}_{R})/{Q}_{0}$ were determined from the mixing ratios measured for the 3/2[411] and 5/2[532] rotational bands in $^{101}\mathrm{Zr}$ and $^{103,105}\mathrm{Mo}$. The combination of this quantity with the measured $g$ factors permitted the separation of the particle-rotor parameters ${g}_{K}$ and ${g}_{R}$ for each band. The comparison of the extracted ${g}_{K}$ factors to Nilsson model predictions confirms current band assignments, and this agreement is consistent with an axially symmetric picture of these nuclei at low spins. The possible effect of triaxial deformation on the measured magnetic moments was investigated in the rigid triaxial rotor-plus-particle framework. The calculations suggest that triaxial deformation plays a stronger role in the Mo than in the Zr isotopes, but that triaxiality is likely to be dynamic. The extracted ${g}_{R}$ factors are consistently smaller than the $Z/A$ limit, in agreement with observations in neighboring even-even nuclei.