Coherent transients in molecular gases

Abstract

Coherent transient phenomena can be generated by the abrupt changes of parameters either of the electromagnetic field or of the matter. Comparative analysis of these two approaches, made on the base of experimental research in molecular gases SF6, 15NH3, HFCO and 13CH3F, excited by the radiation of CW CO2 and 13CO2 lasers, is presented. The first approach of photon echo (and its modifications) generation, based on electro-optic pulses formation from the resonant CW exciting radiation, has proven to be successful for intense infrared molecular transitions. The coherent responses are sufficiently powerful to be applied in high resolution spectroscopy, the spectral markers creation ,and molecular collisions investigations. However, this technique is not very effective for the free polarization decay investigations. Another approach based on the Stark switching molecular levels of polar gas, irradiated by CW laser, was demonstrated for free polarization decay and photon echo generation in 13CH3F. Free polarization decay has shown the pronounced frequency shift because of dynamic Stark effect in the CW radiation field. This specific feature of coherent transients, created by Stark switching, limits the high resolution spectroscopy by the low intensity range of exciting radiation. From other viewpoint, it gives unique possibility to investigate coherent transients generated at the dressed molecular levels.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.