Chemistry of large laser sparks.

Abstract:
Single d1 kJ pulses from a high-power laser will be focused into molecular gases to create large laser sparks. This will provide a unique way to mimic the chemical effects of high-energy-density events in planetary atmospheres (cometary impact, lightning) matching the natural energy-density and plasma-volume scaling of such events in a fully-controlled laboratory environment. The many chemical reactions initiated by laser-induced dielectric breakdown (LIBD) in both neat molecular gases and in mixtures with compositions related to the study of the chemical evolution of the Earth's early atmosphere will be systematically studied. The processes responsible for the chemical action of laser sparks will be identified and investigated. The results of our high-energy single-pulse experiments will be compared with results for many low-energy pulses from high-repetition-rate lasers, where reaction products from earlier pulses may undergo additional reactions due to LIDB by later pulses.