Study of ground-state titanium ion velocity distributions in laser-produced plasma plumes

The velocity distribution of ground-state titanium ions within a low-temper ature plasma resulting from the laser ablation of a titanium target has bee n investigated. A KrF excimer laser was focused onto the target at moderate fluences (<10 J cm(-2)) in vacuum (similar to 2 x 10(-5) Torr). Time-of-fl ight distributions were determined as functions of distance from target and laser fluence using absorption spectroscopy. The results were found to be described consistently by a Maxwell-Boltzmann distribution with zero flow v elocity. The most probable velocity was found to scale with the square root of the incident laser fluence. (C) 1999 American Institute of Physics. [S0 003-6951(99)01723-4].