74,76,78,80,82Se by inelastic scattering of 64.8 MeV protons.

Abstract

The inelastic scattering of 64.8 MeV protons has been studied on the stable even $^{74\mathrm{\ensuremath{-}}82}\mathrm{Se}$ isotopes. The inelastically scattered protons were momentum analyzed in a magnetic spectrograph with a resulting energy resolution of approximately 20 keV. Levels up to the excitation energy of about 5 MeV were investigated. Many new levels were observed for the isotopes studied. The angular distributions obtained were compared with the predictions of distorted-wave Born approximation and coupled-channels calculations and a number of new spin assignments were proposed. Several ${4}^{+}$ states with comparable strengths were found at about ${E}_{x}$=2.0--5.0 MeV, showing large fragmentation of octupole and hexadecapole transition strengths, in contrast to the case of Zn isotopes. The distributions of the transition strengths for the ${2}^{+}$, ${3}^{\mathrm{\ensuremath{-}}}$, and ${4}^{+}$ states were compared with the theoretical calculations based on the random-phase-approximation model for spherical nuclei.