VELOCITY DISTRIBUTIONS OF MOLECULES EJECTED IN LASER-ABLATION

Based on the results of molecular dynamics simulations, we propose an analytical expression for the velocity distributions of molecules ejec ted in laser ablation. The Maxwell-Boltzmann distribution on a stream velocity, commonly used to describe the measured velocity distribution s, is modified to account for a range of stream velocities in the ejec ted plume. The proposed distribution function provides a consistent de scription of the axial and radial velocity distributions. The function has two parameters that are independent of the desorption angle and h ave clear physical meaning, namely, the temperature of the plume and t he maximum stream velocity or velocity of the plume propagation. (C) 1 997 American Institute of Physics.