Alpha-particle emission as a probe of nuclear shapes and structure effects in proton evaporation spectra

Abstract

Emission barriers and subbarrler anisotropies from a decay of Sn* and Y'b* compound nuclei are examined in the light of calculations incorporating deformation effects in the decay process. For the Yb* systems deformation which increases with spin is necessary to explain the data. For the Sn* systems the spectral shapes and auisotropies can be explained without deformation. For systems lighter than Sn this probe is not sensitive to the deformation. Energy spectra and angular correla-52 34 82tions of evaporated protons from the Cr( S, 2n2p) Sr reaction were measured in coincidence with discrete transitions. Large shifts in proton spectra were observed when high spin states in different rotational bands are populated. They are interpreted as due to near-yrast stretched proton emission preferentially populating the yrast hand by subbarrier protons. Simulations show that channel selected proton spectra cannot be used as probes of deformation.