Photoacoustic Raman Spectroscopy of Gases |
| |
Authors: | J J Barrett |
| |
Institution: | Corporate Technology Allied Corporation , Mt. Bethel, New Jersey, 07060 |
| |
Abstract: | Abstract Photoacoustic Raman spectroscopy (PARS) 1] is a nonlinear spectroscopic technique based upon the selective population of a given energy state of a system by the process of coherent Raman amplification (stimulated Raman scattering). The necessary conditions for this process are: (1) the transition involving the initial and final energy levels must be Raman-active, i.e., the transitions must involve a change in the molecular polarizability; and (2) the frequency difference of the two incident laser beams must be adjusted to equal the frequency of this Raman-active transition. Since the occurrence of a Raman spectrum depends on a change in polarizability of the molecule and not on the presence of a transition dipole moment, Raman-active transitions can occur for molecules that have no infrared spectrum. This fact makes PARS a particularly attractive analytical technique for studying molecules which have no infrared spectrum The PARS technique was first demonstrated experimentally using |
| |
Keywords: | |
|
|