Selection rule effects in electronic excitations of chemisorbed molecules as studied by energy loss spectroscopy

Selection rule effects associated with long-range transition dipole scattering can be significant in electron energy loss spectroscopy (ELS) for loss energies up to ∼10-12 eV (or higher) on a variety of metal and semiconductor surfaces. These effects will appear in ELS studies of the electronic excitations of chemisorbed molecules; in particular, selection rule effects will suppress the intensity of certain low-lying valence transitions in several cases of current interest in chemisorption. © 1978.