Inelastic electron scattering from collective levels of Gd154

Differential cross sections for elastic and inelastic scattering of electrons by Gd154 have been measured for states below 1 MeV of excitation. Levels of three major collective bands are studied: the 0+, 2+, 4+, and 6+ rotational states; the 2+ gamma vibration; and the 0+ and 2+ beta vibrational levels. This study includes the first electron scattering measurements of a beta vibration. Extraction of these small inelastic cross sections required improvements in momentum resolution and detector response uniformity. Data from the rotational band are compared with axially symmetric Hartree-Fock predictions. Disagreement between the measurements and Legendre projections of the calculated density, particularly for higher multipolarity states, indicates a breakdown in the Hartree-Fock approximation or the rotational model. Small amplitude vibrations of the nuclear shape derived from the measured rotational densities agree well in shape when independently normalized to the cross section strength for both the beta and gamma 2+ vibrations, substantiating their geometrical interpretations. Once transition strength of the beta band is set, however, the strength and shape of the 0+ beta is not correctly predicted, indicating a more complicated configuration.