LASER OPTOGALVANIC SPECTROSCOPY OF ARGON IN THE WAVELENGTH REGION 605-740 NM

Two-photon optogalvanic transitions in Ar glow discharge with Nd: YAG laser pumped dye laser excitation in the frequency range 13520-16520 c m(-1) has been studied using linear and circular polarization. The int ensities of two-photon optogalvanic transitions are very sensitive to changes in the incident laser power which is not the case with one-pho ton transitions. Intensity ratio for circular and linear polarized lig ht for two photon transitions 6s'[1/2]degrees 1 <-- 4s[3/2]degrees 2, 6s'[1/2]degrees 0 <-- 4s[3/2]degrees 2, and 5d[1/2]degrees 0 <-- 4s[3/ 2]degrees 2, 5d[1/2]degrees 1 <-- 4s[3/2]degrees 2 are quite different from the other two-photon transitions. This has been explained as due to near one photon resonance of 4p'[3/2]1 level for the first pair an d 4p'[1/2]1 for the second pair of transitions. The ratio of optogalva nic intensity for circular to linear polarized light has been theoreti cally estimated and compared with the observed results.