An analytical model for three-dimensional laser plume expansion into vacuum in hydrodynamic regime

Dynamic of a dense, laser-produced vapor plume is studied. The analysis is based on the special solution of gas dynamics equations that describes the expansion of an ellipsoidal gas cloud into vacuum. This solution is employed to explain the apparent ‘rotation’ of the cloud — the so called ‘flip-over effect’. The flux of atoms onto the substrate and the film thickness profile are calculated using the model. The present model can be used for the interpretation of the time-of-flight spectra of atoms in laser ablation, and for the description of the shape of vapor cloud expanding into an ambient gas.