Excitation vs electron emission near the kinetic thresholds for grazing impact of hydrogen atoms on LiF(001)

The coincident measurement of projectile time-of-flight spectra and number of emitted electrons for grazing scattering of fast H⁰ atoms from a LiF(001) surface allows us to investigate electronic excitation and emission processes, including those without emission of electrons. Using this method, we are able to study very small electron emission yields and thus kinetic threshold behavior for projectile induced electronic processes. We observe different onsets for electron emission and electronic excitation of the target, providing important conclusions on the relevant interaction mechanisms. Near the kinetic thresholds, inelastic processes are found to be dominated by production of surface excitons.