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

The velocity distribution of ground-state titanium ions within a low-temperature plasma resulting from the laser ablation of a titanium target has been investigated. A KrF excimer laser was focused onto the target at moderate fluences (<10 J cm−2) in vacuum (∼2×10−5 Torr). Time-of-flight 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 velocity. The most probable velocity was found to scale with the square root of the incident laser fluence.