Energy Transfer between Excited Atomic, Molecular and Ionic Species in a Laser Produced Spark in Ar–O2 and Ne–O2 Gas Mixtures

We have investigated laser induced breakdown in Ar O2 and Ne O2 gas mixtures with different O2 compositions to study possible energy transfer between excited atomic and ionic species (Ne, O, Ar, Ne, Ar, O) in these gas mixtures. Laser pulses of 5 ns duration with a repetition rate of 10 Hz from a frequency doubled Nd: YAG (λ = 532nm) delivering up to 75 mJ energy per pulse were used to create sparks. Energy transfer was inferred from the changes occurring in the intensities of specific atomic and ionic transitions in the respective emission spectra of Ar O2 and Ne O2 gas mixtures compared with the corresponding intensities in the spectra of pure Ar, Ne and O2 gases. Strong evidence of energy transfer from Ar and Ne to O was recorded. High lying metastable levels of Ar and Ne are believed to play important roles in this collisional energy transfer.