24 - Raman spectroscopic studies of proton conductors

Summary

Introduction

Raman scattering spectroscopy is a versatile and powerful technique for studying composition, structure and dynamics in a wide variety of condensed phases. Transitions between vibrational states are measured in the usual Raman scattering experiment, as in an infrared transmission experiment. However, the selection rules governing Raman scattering differ from those of infrared absorption, so the two techniques should be regarded as complementary. Since the scientific literature regarding the application of Raman spectroscopy to studies of proton conductors is quite extensive, this chapter will not attempt to provide a comprehensive review. Rather the different kinds of structural and dynamical information which can be obtained from these studies will be surveyed, with examples given which illustrate the versatility and power of the technique.

In the next section, the theory of the Raman effect will be briefly reviewed, followed by Section 24.3, the application of Raman spectroscopy to studies of proton conductors. The description of structural information will be divided according to data obtained from band frequencies, intensities, bandwidths, and studies of phase transitions. The chapter will then conclude with several illustrations of dynamical information which can result from an appropriate analysis.

The Raman effect

Raman scattering has been the subject of numerous excellent reviews and will be only briefly summarized here. In general terms, an external electromagnetic field interacts with matter, inducing an oscillating electric moment which acts as a source of scattered electromagnetic radiation.