TEMPORAL AND SPATIAL TAO EMISSION GENERATED FROM UV LASER-ABLATION OFTA AND TA2O5 IN OXYGEN AMBIENT

The optical emission spectra of the plume produced by UV laser ablatio n of Ta and Ta2O5 targets in oxygen ambient are presented. Line assign ments indicate the presence of the excited Ta(I), Ta(II), and TaO in t he plume. At higher oxygen pressure, a single peak appears in the TaO emission spectrum from the laser ablation of Ta while two peaks corres ponding to a fast and a slow component of TaO emission are observed fr om the laser ablation of the Ta2O5 target by time-resolved emission sp ectroscopy. The delay times after laser pulse corresponding to two com ponents of TaO emission from the laser ablation of Ta2O5 have been inv estigated as a function of oxygen pressure, laser fluence, and observa tion distance from the target surface. The two components of TaO emiss ion could be attributed to different pathways for the generation of ex cited TaO molecules. A blast wave model is proposed to describe the be havior of the excited TaO in the plume of laser ablation of Ta2O5.