Optoacoustic Raman spectroscopy of molecular gases

Theoretical and experimental investigations were made of the advantages and drawbacks of a new nonlinear laser method of optoacoustic Raman spectroscopy. The physical processes underlying this spectroscopy are discussed. An opposed geometry of the interaction of light beams in optoacoustic Raman spectroscopy is proposed and it is shown that this geometry can increase by at least an order of magnitude the output signal compared with the unidirectional interaction scheme used earlier. An analysis is made of the influence of saturation of the investigated Ramanactive transition by two-frequency pumping on the information which can be extracted from the spectra. It is shown experimentally that optoacoustic Raman spectroscopy is highly sensitive and selective when it is applied to pure molecular gases and their mixtures.