(p, p′γ) Angular Correlations at Low Energy

Abstract

At an incident proton bombarding energy of 6.5 Mev, angular correlations were measured between protons scattered inelastically from various even-even nuclei and the decay gamma rays from the first excited states of these nuclei. The angular correlation experiments reported are C/sup 12/(p,p' gamma ) 4.4 Mev, Li/sup 7/(p,p' gamma ) 0.48 Mev Cr/sup 52/(p,p' gamma ) 1.44 Mev, Ne/sup 20/(p,p' gamma ) 1.63 Mev, Si/sup 28/(p,p' gamma ) 1.78 Mev, and S/sup 32/(p,p' gamma ) 2.25 Mev, which were done for proton detector angles of 60 deg , 90 deg , and 120 deg . The measured angular correlation functions are all of the form A + B STAsin/sup 2/2( theta -- theta /sub 0/)!, where theta /sub 0/ is the axis of symmetry. None of the symmetry directions agreed with predictions of the simple directreaction theories. However, the symmetry direction for the correlation functions changed with proton detector angle for the experiments on C/sup 12/, Ne/ sup 20/, and S/sup 32/; for the experiment of Si/sup 28/ the angular correlation functions were symmetric about 90 deg , independent of proton detector angle. The results of the angular correlation experiments appear to be consistent with a collective interaction involved inmore » these direct-type reactions rather than a nucleon-nucleon type collision at the nuclear surface. (auth)« less