Soft giant dipole mode of 11Li.

Abstract

The low-lying electric dipole distribution for {sup 11}Li is examined in detail in a large basis nonspurious shell model which includes up to 3{h bar}{omega} of excitation. A very strong enhancement of the {ital E}1 strength between 1 and 4 MeV of excitation is predicted when Woods-Saxon single-particle wave functions are used. The relativistic Coulomb excitation cross section is underestimated. However, an analysis of the contributions to the {ital E}1 matrix elements indicates that small changes in the structure of the low-lying states can lead to a significant increase in the predicted {ital E}1 strengths, so that excitations normally omitted from shell-model calculations are not necessarily needed to explain the anomalous Coulomb cross section.