Numerical analysis of time-of-flight distributions of neutral particles for pulsed laser ablation of binary substances into vacuum

摘要

Direct Monte Carlo simulation of the laser-induced plume expansion under pulsed laser evaporation of binary substances into vacuum has been performed. Analysis of separation of the mixture components has been carried out for a wide range of the problem parameters: the mass ratio, the number of evaporated monolayers, and the initial mixture concentration. Special attention has been paid to examination of the mixture separation and changing the mixture concentration for particles passing through the time-of-flight detector located on the normal to the evaporating surface. Universal dependences of the energy and concentration ratios of species passing through the time-of-flight detector on the number of evaporated monolayers have been obtained. It is shown that these dependences can be used for analysis of any experimental data independently on the concentration ratio. The obtained relations well correlate with known numerical and experimental data on gas phase separation under pulsed evaporation into vacuum. The obtained results allow to completely determine the conditions at the evaporating surface (the surface temperature, the number of evaporated monolayers, and the initial mixture composition) from experimentally measured time-of-flight distributions of neutral particles.