Shears mechanism in109Cd

Lifetimes of high-spin states in two $\Delta I=1\mathrm{}$ bands and one $\Delta I=2\mathrm{}$ band in ${}^{109}\mathrm{Cd}$ have been measured using the Doppler shift attenuation method in an experiment performed using the ${}^{96}\mathrm{Zr}{(}^{18}\mathrm{O},5n)$ reaction with the GAMMASPHERE array. Experimental total angular momenta and reduced transition strengths for both $\Delta I=1\mathrm{}$ bands were compared with tilted axis cranking (shears mechanism) predictions and the $\Delta I=2\mathrm{}$ band with principal axis cranking predictions, based on configurations involving two proton $g_{9/2}$ holes and one or three valence quasineutrons from the $h_{11/2}$ and mixed $g_{7/2}{/d}_{5/2}$ orbitals. Good overall agreement for angular momentum versus rotational frequency has been observed in each case. The $\Delta I=2\mathrm{}$ band is shown to have a large ${\mathcal{J}}^{\mathrm{}\left(2\right)\mathrm{}}/B\left(E2\mathrm{}\right)\mathrm{}$ ratio suggestive of antimagnetic rotation. Additionally, both dipole bands show a decreasing trend in $B\left(M1\mathrm{}\right)\mathrm{}$ strength as a function of spin, a feature of the shears mechanism. The experimental results are also compared with a semiclassical model that employs effective interactions between the proton holes and neutrons as an alternate interpretation for the shears mechanism.