Time-resolved line shape studies of Nd : YAG laser-induced microplasmas arising from gold surfaces.

A systematic study of the time evolution of the line shape of radiation emitted by a gold plasma and an exact line intensity calculation was carried out. The emission of the hot and dense plasma produced by a Q-switched Nd:YAG laser in atmospheric air was measured by a time-gated optical multichannel analyzer. Asymmetric Lorentz-type profile equations were tested for two gold lines (406.51, 389.79 nm) as a function of time. A strong broadening, asymmetry and shift is observable up to 800-1000 ns after the laser pulse. Spectral profiles of the delayed (with 0.8-1.0 micros) and time-integrated (gate time of 2.5 micros) measurements were found to be well represented by a symmetric Lorentz-type curve.