Capture and loss of valence electrons during low-energy proton scattering from rare-gas solid surfaces

Energy spectra of low-energy (10–500 eV) protons scattered from solid Ar, Kr and Xe surfaces exhibit up to six energy-loss peaks due to electron–hole pair excitation. They are caused by the electron promotion mechanism via the transient molecular orbitals and the neutralization/reionization sequence of proton along the trajectory involving surface few layers in the rare-gas solids. The yield of proton from Xe, though smaller than that from Ar by almost two orders of magnitude, increases markedly when Xe is intermixed with Ar since the Xe+ 5p hole (or the H+ 1s hole), which is delocalized due to some covalent orbital hybridization in solid Xe, tends to be localized in the intermixing layer.