Systematics of the shears mechanism in silver isotopes

Abstract

A systematic investigation of the shears mechanism in silver isotopes has been carried out. Lifetimes have been measured by means of the Doppler-shift attenuation method for states in two magnetic dipole ($M1$) bands in $^{105}\mathrm{Ag}$ and one each in $^{103}\mathrm{Ag}$ and $^{106}\mathrm{Ag}$. Experimental total angular momenta and reduced transition strengths for these bands have been compared with the predictions of the tilted axis cranking (TAC) model with configurations involving one ${g}_{9/2}$ proton and quasineutrons from the ${h}_{11/2}$ and ${g}_{7/2}$ or ${d}_{5/2}$ orbitals. There is good overall agreement for both the total angular momenta and reduced transition strengths. The deduced $B(M1)$ strengths, which are a sensitive probe of magnetic rotation, show a decrease consistent with TAC predictions for one $M1$ band in $^{105}\mathrm{Ag}$ and in $^{106}\mathrm{Ag}$, confirming the shears mechanism as the means of excitation. Furthermore, the staggering in the transition energies in $^{103}\mathrm{Ag}$ and absence of regular sequences of $M1$ transitions for $N\ensuremath{\le}56$ suggest that $N=56$ is the lower boundary for the appearance of the shears mechanism in this mass region.