THE DISTRIBUTION OF THE ROTATIONAL TRANSITION STRENGTH IN WARM NUCLEISTUDIED THROUGH GAMMA-RAY CORRELATIONS

The study of damping of rotational motion applying the rotational plan e mapping (RPM) method is presented and discussed. The aim of this tec hnique is to extract the distribution of the rotational transition str ength from an analysis of the shape of the ''central valley'' of two- and three-dimensional gamma-ray spectra. The method is applied to a tr iple gamma-coincidence data set of Tm-162,Tm-163 nuclei formed in Cl-3 7+Te-130 reactions. The rotational transition strength is obtained as a function of rotational frequency for selected regions of entry state s, and the width is found to be rather constant and approximately equa l to 80 keV. This value is significantly smaller than the value predic ted theoretically for the rotational damping width Gamma(rct). Also th e ratio between the observed depth and width of both the 2D and 3D val leys does not agree with the simple model adopted in the RPM method, T hese discrepancies point to the presence of both a wide and a narrow c omponent in the distribution of rotational strength as extracted by th e RPM method. The analysis of simulated spectra obtained on the basis of realistic band-mixing calculations, including residual interactions , confirms this behaviour.