The theory of photonucleation kinetics

Abstract

The paper deals with the kinetic theory of cluster formation of a condensed phase in supersaturated vapor under laser radiation. Two channels of the photonucleation kinetics are defined. The kinetic equations for the distribution function of the cluster size are derived using the methods of nonequilibrium statistical thermodynamics. The first channel involves direct heat impact of the laser radiation on the cluster of a condensed phase. The second channel of photonucleation deals with resonance excitation of vapor molecules under the effect of laser radiation at the specific of wavelength and deactivation of internal degrees of freedom of the vapor molecules during collisions with the cluster surface. The important dimensionless groups of physical parameters, which characterize these channels of photonucleation, are obtained. Some results of a numerical investigation of the steady-state photonucleation kinetics are presented. In particularly, it is shown in the frame of the discussed physical models, that laser radiation usually decreases the nucleation rate. For cases where the second mechanism (channel) of photonucleation is the most important, the theory predicts the existence a state when the opposite effect takes place, i.e. the nucleation rate is enhanced.