Resonance electron scattering by adsorbed molecules: [formula omitted] resonance energy versus bond length

Abstract

This paper explores the relationship between the energy of the σ ∗ negative ion resonance, observed in the cross-section for vibrational excitation of small molecules in electron energy-loss spectroscopy (EELS), and the intramolecular bond length. On the basis of experimental results assembled from studies of electron scattering by both free and adsorbed molecules containing the CO group, we find an approximately linear empirical correlation between the resonance energy and the CO bond length. This correlation is accurately reproduced by multiple-scattering X α calculations for the free CO molecule as a function of bond length, suggesting the possible determination of molecular bond lengths from the σ ∗ resonance energies obtained in EELS. Similar calculations are reported for N 2 and O 2 in addition to CO.