Collisional population redistribution of radiatively excited levels of Na in nine acetylene-O 2 flames

Abstract

Thermally assisted fluorescence from the higher levels of Na was detected upon excitation of the 3S → 3P single photon resonance transition and 3S → 4D and 3S → 5S two-photon resonance transitions with an excimer pumped tunable dye laser. The Na atomic population distributions observed in the nine C 2H 2/O 2/Ar or C 2H 2/O 2/N 2 flames that range in temperature from 2000 to 2500 K indicated that partial Boltzmann equilibrium is not reached during the $ ̃ 5 ns laser pulse. Larger deviations from partial Boltzmann equilibrium are reported for the Ar-diluted flames than for the N 2-diluted flames. These results indicate that Na under $ ̃ 5 ns excitation will not produce valid local flame temperatures.