INFRARED DIODE-LASER PROBING OF METHANE IN EXCIMER-LASER PHOTOLYSIS OF PYRUVIC-ACID

The photodissociation of pyruvic acid at 193 nm has been studied and o ne 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 nu(4) band], t he progress of the reaction was monitored. The quantum yield of format ion of methane = 0.09 +/- 0.01 and was further corroborated by a simpl e measurement of pressure changes following the photolysis. The second ary photolysis of the photoproduct acetaldehyde via the established ro ute was found to be negligible. This result may help to account for th e energetics of the photodissociation process by a 6.4 eV excimer lase r photon. The possibility of using this technique to examine the nasce nt methane molecule in real-time domain to gain better insight of the dissociation dynamics is also indicated.