Infrared diode laser probing of methane in excimer laser photolysis of pyruvic acid

Abstract

The photodissociation of pyruvic acid at 193 nm has been studied and one of the photoproducts, methane, was detected using an infrared diode laser absorption probe technique. Using second-derivative absorption spectroscopy at 1346.326 cm^-1[R ^(-)(7) transition in v4 band], the progress of the reaction was monitored. The quantum yield of formation of methane = 0.09 ± 0.01 and was further corroborated by a simple measurement of pressure changes following the photolysis. The secondary photolysis of the photoproduct acetaldehyde via the established route was found to be negligible. This result may help to account for the energetics of the photodissociation process by a 6.4 eV excimer laser photon. The possibility of using this technique to examine the nascent methane molecule in real-time domain to gain better insight of the dissociation dynamics is also indicated.