Electron-molecule dynamics at surfaces

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This article discusses the role of short-lived negative ion states in molecule-surface dynamics. Such negative ion resonances may be produced either by electron capture in electron beam impact on adsorbed molecules, e.g. in high resolution electron energy loss spectroscopy or electron stimulated desorption, or by electron capture from the surface itself, e.g. in photodesorption or molecular beam scattering. The prime purpose of the review is thus to highlight the similarities in the fundamental physics underpinning a variety of apparently disparate surface processes, and to promote cross-fertilisation between these different areas. In view of this aim, and the broad scope of the subject, no attempt is made to present a complete review of each of the fields considered. Instead, a cluster of examples is chosen, primarily from recent experimental studies, to illustrate the role played by negative ion resonance states in each of the dynamical processes; specifically, vibrational excitation in electron scattering, electron stimulated desorption, photon stimulated desorption, dissociative adsorption, negative ion formation and vibrational excitation in molecular beam scattering, and recombinative molecular desorption. The article concludes with a discussion of possible future developments in the field.