Following laser-induced plasma stoichiometry with atomic absorption spectroscopy

Atomic absorption spectroscopy was used to measure the absolute vanadium and titanium masses present as neutral atoms in the plume formed by laser ablation of a titanium alloy sample. At delays between two and twenty microseconds, the absolute masses and temperatures were measured with time-resolved Boltzmann plots under pure helium and an 80:20 He/O-2 mixture. The Boltzmann plots, which include the ground term (in contrast to emission-based measurements), produced high-quality estimates of the plasma composition. Under helium, the metal vapors persisted beyond the longest similar to 20 mu s delays measured. The V:Ti stoichiometry was approximately as expected from the nominal sample composition at all times under He. However, under He/O-2, the atomic vapor disappeared entirely in under 10 is and the stoichiometry became more enriched in vanadium at increasing delays. This enrichment is interpreted in terms of the difference in first oxide bond energies of the two metals. There was evidence of loss of metal even under helium within the investigated 20 mu s window.