Spectroscopy of high-spin states in 217Ra

Abstract

The high-spin level structure of 217Ra has been established up to a spin of ( 47 2 ) by means of in-beam γ-ray and conversion electron spectroscopy with ( 12,13C, xn) reactions on 208Pb. Positive parity levels up to case27 2 + and negative-parity states up to ( case31 2 − ) can be qualitatively understood in terms of neutron excitations arising out of the shell-model configurations v g 3 9 2 , v g 2 9 2 i 11 2 and v g 2 9 2 j 15 2 . The isomeric 33 2 + state at 2.4 Me V and the levels above it require both neutron and proton excitations. The El transitions between the negative-parity and the v g 3 9 2 states suggest the presence of octupole-deformed configurations. Our shell-model calculations provide only a qualitative description of the levels. The experimental level spacings and their moderate agreement with the calculated ones suggest also the onset of deformation and of collective vibrational characteristics.