Time-dependent Hartree-Fock calculations ofKr86+La139atElab=505, 610, and 710MeV

Abstract

Time-dependent mean-field calculations, using the axially symmetric, rotating frame approximation, have been performed for the reaction $^{86}\mathrm{Kr}$ + $^{139}\mathrm{La}$ at ${E}_{\mathrm{lab}}=505, 610, \mathrm{and} 710$ MeV. This is a new intermediate mass region for scattering heretofore relatively unexplored in time-dependent Hartree-Fock studies, and we obtain some results not observed in either lighter or heavier nuclear systems. At all three energies the final kinetic energy loss and angular dependence are in fair agreement with experiment, the most serious discrepancies occurring for the large-angle (small angular momentum) fully damped events whose calculated kinetic energies are about 50 MeV above the experimental ridge on the Wilczy\ifmmode \acute{n}\else \'{n}\fi{}ski plots. Fusion is not seen at the two lower energies studied. However, at ${E}_{\mathrm{lab}}=710$ MeV fusion is observed for angular momenta from 0 to $65 \ensuremath{\hbar}$, and just beyond the upper fusion limit we observe positive-angle scattering, in contrast to the negative-angle scattering always seen beyond the fusion limit for reactions of lighter ions. It is suggested that the fusion behavior for this reaction may be a definitive test of whether heavy-ion scattering is better described by a microscopic mean-field theory or macroscopic fluid dynamics. At ${E}_{\mathrm{lab}}=710$ MeV emission of alpha-like particles from the neck at scission is observed for a small range of angular momenta near $100 \ensuremath{\hbar}$.NUCLEAR REACTIONS $^{86}\mathrm{Kr}$+$^{139}\mathrm{La}$ at ${E}_{\mathrm{lab}}=505, 610, \mathrm{and} 710$ MeV in the timedependent Hartree-Fock approximation. Fusion and strongly damped collisions. Pre-equilibrium alpha-like emission from the neck.