Time-resolved spectroscopic diagnostic of laser-induced plasma on Germanium targets

Abstract

Time-resolved optical emission measurements have been made in laser-induced plasma plumes following CO2 pulsed-laser (10.591 lm, 64 ns and intensity from 0.27 to 4.9 GW cm#2;2) irradiation of germanium targets. The temporal behavior of Ge atoms and ionized excited species Ge3þ, Ge2þ, and Geþ is reported. The results show a faster decay of the continuum emission and Ge3þ, Ge2þ ionic species than in the case of Geþ and neutral Ge atoms. The velocity distributions for Ge3þ, Ge2þ, Geþ, and Ge species are obtained from time-of-flight measurements. Electron density in the laser-induced plasma was estimated from the analysis of spectral data at various times from the CO2 laser pulse incidence. From the intensity decay with the delay time for Geþ, Ge2þ, and Ge3þ, we estimated the three-body electron-ion recombination rate constants for these species. VC 2011