Model for laser ablation plume expansion in gas

A simple model for laser ablation plasma plume expansion in a background gas is presented. The expanding plume is approximated by a semi-ellipsoidal shell of infinitesimal thickness and with a mass corresponding to the amount of background gas that has been snowploughed by the shell as it expands. Furthermore, the internal pressure of the plume and external pressure of the background gas are taken into account. Electrical probe measurements of ns laser ablation of Ag were used to map out the angular dependence of plume expansion in argon at various pressures and the results compared with model predictions.