Precompound decay calculations for reactions induced by 10–100 MeV/nucleon heavy ions

Abstract

The Boltzmann master equation model has been applied to the question of precompound nucleon deexcitation of reactions induced by 10–100 MeV/nucleon (c.m.) heavy ions. Test systems of ${}_{}{}^{16}{}_{}{}^{}$O${+\mathrm{}}^{60}$Ni and ${}_{}{}^{27}{}_{}{}^{}$Al${+\mathrm{}}^{86}$Kr were selected. Experimental neutron spectra in coincidence with evaporation residue and fission fragments from the ${}_{}{}^{20}{}_{}{}^{}$Ne${+\mathrm{}}^{165}$Ho system (due to Holub et al.) were reproduced quite well by the master equation with exciton numbers between 20 and 23. Exciton values of projectile mass and projectile mass plus 3 were therefore used in the extrapolations of the master equation. Results show major fractions of the excitation and up to 35 nucleons removed during the coalescence-equilibration period. The linear momentum transfer predicted by the master equation is shown to be in good agreement with a broad range of data. Calculations are provided as to the range of angular momenta which may be carried off by the precompound cascade.