Applications of Raman Spectroscopy to Heterogeneous Catalysis

A number of reviews have recently appeared in the literature concerning the Raman spectroscopy of catalytic systems. The purpose of this chapter is not to review the literature, but to demonstrate what is currently achievable in Raman spectroscopy of heterogeneous catalysis. The theory of the Raman effect and its relationship to signal intensity are presented in Section 2. Point-group symmetry and the Frequency/Length/ 

Strength (FLS) empirical approach are discussed in Section 3 as methods for determining the molecular structures of metal-oxide species from their Raman spectra. The state-of-the-art in Raman instrumentation as well as new instrumental developments are discussed in Section 4. Sampling techniques typically employed in Raman spectroscopy experiments, ambient as well as in situ, are reviewed in Section S. The application of Raman spectroscopy to problems in heterogeneous catalysis (bulk mixed-oxide catalysts, supported metal-oxide catalysts, zeolites, and chemisorption studies) is discussed in depth in Section 6 by selecting a few recent examples from the literature. The future potential of Raman spectroscopy in heterogeneous catalysis is discussed in the fmal section. 

Observations of the Raman effect were first reported in 1928 by Raman and Krishnan in the course of work carried out on the light-scattering ability of molecules  

The Raman effect depends on the polarizability of the molecule and the dipole moment induced or distorted by the electric field of the incident light. Given the 

The induced electric dipole moment P responsible for the Raman signal can be related to the electric field E of the incident radiation by the power series 

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Wachs, I.E. and Hardcastle, F.D. Applications of Raman spectroscopy to heterogeneous catalysis. In Catalysis. Cambridge The Royal Society of Chemistry, Vol. 10, 1993. 

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