Evidence of a shape transition in even-A Ge isotopes.

Abstract

Cross-section and vector-analyzing-power measurements have been carried out for /sup 70,72,74,76/Ge(darrow ,d) at E/sub d/ = 8 and 16 MeV, (darrow,d') 2/sup +/ at E/sub d/ = 16 MeV, and (parrow,p) and (parrow,p') 2/sup +/ at E/sub p/ = 11.5 MeV. Exploratory measurements of /sup 70,72,74/Ge(darrow,d) at E/sub d/ = 6 MeV have also been performed. The elastic analyzing-power data for A = 70,72 are nearly identical, as are those for A = 74,76, and a sudden decrease in the amplitude of A/sub y/ occurs in going from A = 72 to 74. The inelastic-scattering data also show near identity for the A = 70,72 target nuclei as well as for A = 74,76, with characteristic changes occurring between A = 72 and 74. Coupled-channels calculations have been performed for all four isotopes using a macroscopic form factor employing both vibrational and rotational models. It is found that the anomalous behavior of the elastic-scattering data at E/sub d/ = 16 MeV and at E/sub p/ = 11.5 MeV is by itself not indicative of ground-state shape, but only shows the effects of target excitation on elastic scattering. The 2/sup +/ inelastic-scattering data, however, can be explained only if a vibrationalmore » model is assumed for /sup 70,72/Ge and a prolate symmetric rotational model is assumed for /sup 74,76/Ge. These results are indicative of a shape transition between /sup 72/Ge and /sup 74/Ge, consistent with the conclusions drawn from transfer-reaction measurements.« less