With 2 FiguresVibrational kinetics is concerned with the nonequilibrium conditions and molecular energy distributions over vibrational degrees of freedom. Such conditions arise in many physical phenomena and processes, e.g., in sound propagation, shock waves, gas flows from openings and nozzles, electric discharge gases exposed to corpuscular or electromagnetic radiation, and in different chemical reactions. The nonequilibrium distributions can be either artificially induced (in experiments) or inherent in some natural objects (as in the upper atmosphere of planets and interstellar clouds). Various effects on molecules result in a redistribution of vibrational level populations, which, in turn, may greatly affect the course of physical and chemical processes. Therefore, investigations of vibrational kinetics are of particular importance for different fields of physics and chemistry such as relaxation gas -dynami cs, gas -d is cha rge phys i cs, P 1 asmachemi s try, 1 aser phys i cs and chemi s try, aeronomy, and optics of the earth's upper atmosphere.
Historical OverviewAt a small deviation of the available vibrational energy from the equilibrium value or at high gas temperatures, the vibrational relaxation can be described, with good accuracy, by the harmonic oscillator model. In the early sixties detailed studies of the V-T energy exchange in diatomic gases, and V-V exchange in one-component gas and in binary mixtures of diatomic gases were carried out, using this model. The theory was extended to thermal dissociation at vibrational levels. The results are given in [3.1-8].However, in the middle sixties, due to rapid development of laser physics and molecular vibrational transition lasers, special attention was given to the analysis of vibrational kinetics at low temperatures and large available vibrational energies. The investigation of such regi~es was also stimulated by the problems of plasmachemistry, laser chemistry, and upper-atmosphere physics. The harmonic oscillator model was found to be inadequate for the description of vibrational kinetics under such conditions, since the vibration anharmonicity should be allowed for. The anharmonicity dominates in the production of high vibrational level 47 M. Capitelli (ed.), Nonequilibrium Vibrational Kinetics