LI-LI AZIMUTHAL ANGULAR-CORRELATIONS - A TEST FOR EMISSION FROM A ROTATING SOURCE VERSUS INSTANTANEOUS MULTIFRAGMENTATION

Azimuthal angle correlations have been measured for Li-Li pairs from A r-40 + Au-197, (nat)Ag, (nat)Cu, Al-27 (17A, 27A, and 34A MeV). Many o f these correlations exhibit enhancements at DELTAphi of 0-degrees and 180-degrees, the classical pattern for evaporation from a hot, high-s pin source. A very different pattern is predicted by a simple multifra gmentation model, i.e., a peak at DELTAphi almost-equal-to 60-degrees. This peak is driven by the rapid Coulomb explosion of a nonrotating n ucleus. The latter pattern is not observed experimentally, however, if collective rotation is included in the multifragmentation model, its predictions are more consistent with the observations. Such comparison s can give a promising test for sequential emission from a rotating so urce versus instantaneous explosive multifragmentation, but one needs a very good selection of collision centrality to reduce the role of th e collective rotation. For most of these data the dominant driving for ces seem to be rotational motion perturbed by final-state Coulomb repu lsions for time delays of the order of 10(-22) s between successive em issions of Li fragments.