Commentary on high-resolution electron energy loss spectroscopy

Abstract

Vibrational spectroscopy has made an increasingly important contribution to surface science in recent years. Transmission infrared absorption spectroscopy was the first spectroscopy to be applied to adsorbates (Little 1966; Hair 1967), and it remains one of the best methods for the investigation of surface species on finely divided catalyst materials. However, the development of techniques suitable for single-crystal surfaces was essential for fundamental studies of surface vibrations. Reflection-absorption infrared spectroscopy of surface layers on metal single crystals (Hoffmann 1983) is demanding in sensitivity and spectral range, although the latter has been helped by Fourier transform methods (Baker & Chesters 1982). On the other hand, high-resolution electron energy loss spectroscopy (Ibach & Mills 1982) combines high sensitivity with a very wide spectral range, and the existence of the short-range impact scattering mechanism in addition to long-range dipole scattering makes it possible to observe m any more vibrational modes than those accessible to optical methods in which the surface normal selection rule is severely restrictive. The power of electron energy loss methods has stimulated intense interest in all aspects of surface vibrational spectroscopy, an interest that is reflected by a series of international conferences devoted exclusively to this theme. The preceding papers in this Discussion Meeting illustrate the continuing vigour and development of high-resolution electron energy loss spectroscopy.