Laser diagnostics of materials and chemistry

Several examples are given of the ability of laser-based diagnostic techniques to make noninvasive measurements in hostile environments. Using coherent anti-Stokes Raman scattering both majority and minority species concentrations, as well as temperature, were measured in the hot, high-pressure, particle-laden stream of a coal gasifier. In addition, numerous toxic and corrosive elements in the gasifier stream were identified, but not yet quantified. In addition to providing the capability for making analytical determinations, laser techniques were extensively employed to measure the rates of elementary chemical reactions. Recently, the temperature regime over which such measurements are possible expanded. Although much of the laser diagnostic activity to date has involved investigations of the gas phase, significant information concerning heterogeneous phemomena can still be inferred. For instance, gas-solid reactions can manifest themselves as changes in vapor phase composition.