The nuclear structure of 161,163Ho studied with the ( [formula omitted],α) reaction

Abstract

The 162,164Er( t , α) 161,163Ho reactions have been studied using a beam of 17 MeV polarized tritons from the tandem Van de Graaff accelerator at the Los Alamos Scientific Laboratory. The reaction products were analyzed with a Q3D magnetic spectrometer using a helical-cathode position-sensitive detector in the focal plane. Comparisons of the measured angular distributions of cross sections and analyzing powers with DWBA predictions made it possible to assign spins and parities to a number of previously unknown levels in each residual nucleus. The results are interpreted in the framework of the Nilsson model with pairing and Coriolis mixing effects included. The 7 2 −[523], 1 2 +[411], 3 2 +[411], 7 2 +[404], 5 2 +[413], 5 2 −[532] and 1 2 +[420] bands were observed in both 161Ho and 163Ho. In previous stripping reaction studies anomalously large strengths were reported for the 3 2 3 2 +[411] and 5 2 1 2 +[411] states, apparently because of unusually strong mixing with the 3 2 1 2 +[411] and 5 2 3 2 +[411] states, respectively. In the present work the pickup strengths to these states are also found to be larger than expected. A new Coriolis mixing calculation with revised parameters is capable of explaining part, but not all, of the mixing effects. In particular the very large strength of the 3 2 3 2 +[411] state in 163Ho remains unexplained.