Lifetime measurements of scissors mode excitations in 162,164Dy.

Abstract

The inelastic neutron scattering reaction has been used to populate known ${1}^{+}$ scissors mode states in the deformed rare-earth nuclei $^{162}\mathrm{Dy}$ and $^{164}\mathrm{Dy}$. The electromagnetic decay properties of these states have been examined and the Doppler-shift attenuation method has been used to measure directly the lifetimes of these states. The $M1$ strengths determined are in general agreement with those measured previously in nuclear resonance fluorescence experiments and support the conclusion that these are collective structures; however, a significant discrepancy is found for three states near 3.1 MeV in $^{164}\mathrm{Dy}$. Candidates for ${2}^{+}$ rotational band members have been identified, and a previously suggested $\ensuremath{\gamma}$-ray branch from a spin-1 state to the $\ensuremath{\gamma}$ vibration in $^{164}\mathrm{Dy}$ has been observed.