Laser Raman Spectroscopy of Crystal Powders

The problem of exciting Raman spectra of crystal powders with a laser is examined. Various methods of sample illumination are considered. An expression for the signal-to-noise ratio in the presence of stray exciting flux and fluorescence is derived and discussed. An experimental setup with sample holder, beam positioner, double monochromator, and pulse-counting detection is described. In many cases, fluorescence is the major source of unwanted background. Typical data are given for fluorescence, stray light, and signal-to-noise ratios in Raman lines. The probabilities of making a false observation of a line or missing a real line are discussed.