Emission ofLi8Fragments from Cu, Ag, and Au Irradiated by High-Energy Protons

Thin targets of Cu, Ag, and Au were irradiated in a scattering chamber with 2-GeV protons and the ${\mathrm{Li}}^8$ fragments emitted at various angles were collected in nuclear emulsions. Data were also obtained for ${\mathrm{Li}}^8$ produced in emulsion irradiated directly by 1- to 3-GeV protons. Results are presented on the energy spectra of ${\mathrm{Li}}^8$, on the angular distributions, and on the emission cross sections. These are compared with the results of a detailed Monte Carlo calculation in which it was assumed that the ${\mathrm{Li}}^8$ fragments are evaporated from the excited nuclei remaining after the prompt cascade. There is rough agreement between experiment and calculation for the cross sections, for the peak energies in the spectra, and for some of the spectral shapes. However, the experimental angular distributions are more strongly forward-peaked and the experimental energy spectra in the forward direction are considerably broader than the calculated spectra. Either a substantial fraction of the fragments is emitted by a process other than evaporation, or the emission is by a mechanism intermediate between evaporation and fast fragmentation.