Collisional Quenching and Photochemistry of trans-Glyoxal (3Au) Molecules

The time dependence of phosphorescence from gaseous trans-glyoxal 3Au at relatively low pressures excited by a tunable dye laser has been studied in the presence of pure argon and in gas mixtures containing O2, NO, and di-tert-butyl nitroxide. Apparent quenching cross sections for trans-glyoxal 3Au have been measured for these collision partners at 300°K. Some measurements have been carried out with trans-glyoxal-d2. The magnitudes of the cross sections are discussed in terms of possible photochemical or photophysical quenching. A new model, which is consistent with the known photochemistry and with the quenching rates measured here, is proposed for the photodecomposition of trans-glyoxal 3Au to form CO.