Determination of the Spreading Width for the Collective Transition Strength at Finite Temperature

Abstract

The experimentally observed structure of the $E2$ transitions in the quasicontinuum for $^{168}\mathrm{Yb}$ is analyzed. The valley ridge structure along the ${E}_{\ensuremath{\gamma}1}={E}_{\ensuremath{\gamma}2}$ diagonal in $\ensuremath{\gamma}$-energy correlation spectra has been reproduced by a model simulation in which a spreading of the rotational decay strength ${\ensuremath{\Gamma}}_{\mathrm{rot}}$ is introduced in regions of nuclear excitation energy $U>{U}_{0}$ where the density of bands with slightly differing moments of inertia and alignment is high. The values of ${\ensuremath{\Gamma}}_{\mathrm{rot}}$ and ${U}_{0}$ vary from 75 to 110 keV and from 1.25 to 1.0 MeV, respectively, in the energy range $780<{E}_{\ensuremath{\gamma}}<1160$ keV.