Laser stimulation of chemical reactions and scattered field detection

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Abstract
We propose a model to account for some experimental observations on stimulating effects of light absorption on the rate of unimolecular chemical decomposition for gas phase molecules suffering collisions in a thermal bath. Our model calculations show a maximum in the rate constant when plotted against pressure at constant light intensity. A significant additional rate stimulation is predicted when molecules respond coherently to a laser field. This effect is most pronounced as the efficiency of energy transfer collisions increases. Numerical calculations applied to multilevel systems delineate the effects of temperature, pressure, light intensity, and efficiency of energy‐changing collisions on the chemical rate constant. The dynamic behavior of a two‐level system undergoing chemical decomposition is given in detail. We predict that the unimolecular rate constant appears as a linewidth for a broadened elastic component in the scattered electromagnetic field and the inelastically scattered band intensity is directly proportional to the energy‐changing relaxation time. These scattered field measurements may be useful for measuring rapid chemical reactions and vibrational relaxation times.