The evolution of solid material surface radiated by Q-switched pulse laser has been analyzed. A phenomenological model is presented which divided the action of laser on material into four stages. These stages are independently, relatively and coherently. First, the surface temperature rises initially and then the super-heated solid phase is formed. Second, the micro photo-induced plasma emerges and expends originally. Third, the plasma expends freely while the surface of the material changes from super-heated solid phase into melting phase. Finally, the melting phase of surface volatilizes equilibriumly. This ends up until the surface is solidified. By this way, we have treated the phase changing processes with the theory of thermodynamics and plasma dynamics, and established a set of complete equations which can be calculated numerically. The result points out the optimal conditions and parameters for producing neutral sample atom streams which are necessary for spectrum analysis, and has been compared with the experimental.
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