Non-equilibrium kinetics of clusters growth under laser ablation (I)

Abstract

Clusters with various sizes and compositions can be produced by laser ablation in high vacuum, but the formation mechanism of the clusters under given condition still remains to be understood. In this paper, a kinetic model of clusters formed from laser ablation was suggested with considering different experimental conditions such as ablating laser power, backing pressure, expansion of the laser vaporized plasma, thermal radiation and etc., and numerical solution of the relevant kinetic equation was obtained. According to the calculation, about 8 x 10(-9) mole of particals can be produced from each laser pulse and their initial pressure is about 1. 9 x 10(5) Pa. Mainly due to the diffusion of the particals, formation reaction of the clusters cannot succeed at 7. 85 mu s of the ablation laser pulse, but the yields of different cluster products reach their maxima at first 0. 4 mu s. On the whole, size distribution of the clusters is unvaried after 1. 5 mu s, so the formation reaction actually ends by that time.