The extraction of lifetimes of weakly-populated nuclear levels in recoil distance method experiments

Two analytic techniques are described which extend the conventional analysis of recoil-distance method (RDM) data. The first technique utilizes the enhanced counting statistics of the composite spectrum formed by the addition of all γ-ray spectra recorded at the different target-to-stopper distances employed, in order to extract the lifetimes of levels whose observed depopulating γ-ray transitions have insufficient statistics to permit conventional analysis. The second technique analyses peak centroids rather than peak areas to account for contamination by flight distance dependent background. The results from a recent study of the low-lying excited states in 196,198Pt for those levels whose lifetimes could be extracted by conventional RDM analysis are shown to be in good agreement with those obtained using the new methods of analysis. (orig.)