Structure of low-lying states of 76,78,80,82Se deduced from ( [formula omitted], p′) scattering at 16 MeV

Abstract

Angular distributions of dσ dΩ and A y have been obtained for elastic and inelastic scattering of 16 MeV protons leading to the first two 2 + states and the lowest excited 0 +, 4 + and 3 − levels of 76,78,80,82Se. Results have been analyzed in the coupled-channels framework assuming the vibrational model, the rotation-vibration model, the asymmetric rotational model (ARM) and its extension to β-vibrational states. There is no one model which can describe simultaneously all the data. However, we find from our ARM-based analysis, which provides the best overall description of the even-parity states, evidence for different deformations for the first and second 2 + states. Also we observe that the nuclear structure of 82Se seems to be quite different from that of the lighter isotopes studied. We find, too, that the 3 − levels of 76,78,80Se do not behave as simple vibrational octupole states. Nuclear deformations extracted from the present measurements have been compared with those from earlier (n, n') scattering and Coulomb excitation measurements. Finally, the need for complex and/or deformed spin-orbit potentials is discussed.