Evaporation of Alpha Particles in the Interaction of High-Energy Protons with AgBr

A calculation of the energy spectra, angular distributions, and multiplicities of alpha particles evaporated in the interactions of AgBr with 1- and 2-GeV protons has been performed. A Monte Carlo evaporation calculation was combined with the results of the cascade calculation of Metropolis et al. to obtain these data. Special attention has been paid to the motion of the evaporating nuclei and the calculated spectra are obtained in the laboratory system. Consequently, a direct comparison with experiment is possible. The results are compared with the data of Katcoff and co-workers and good over-all agreement is obtained. In particular, the agreement of the calculated and experimental energy spectra below 15 MeV indicates that it is not necessary to invoke the principle of barrier reduction at high-excitation energies to account for the emission of low-energy $\alpha$ particles. The calculation predicts too few $\alpha$ particles with energies above 25 MeV, and it is concluded that the cascade process accounts, in part, for the high-energy portion of the spectrum.