title: Photochemistry of glycolaldehyde in cryogenic matrices.
abstract: The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH3OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H2CO and HCO fragments are seen. Calculations of the potential energy surfaces of S0, S1, and T1 states--to analyse the torsional deformations which are involved in the isomerization process--and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH3OH molecular channel is a minor process, as in the gas phase.
authors.affiliation: Institut des Sciences Moléculaires d'Orsay, CNRS UMR 8214, Université Paris-Sud, 91405 Orsay, France.
authors.forename: W
authors.initials: W
authors.lastname: Chin
authors.affiliation: Institut des Sciences Moléculaires d'Orsay, CNRS UMR 8214, Université Paris-Sud, 91405 Orsay, France.
authors.forename: M
authors.initials: M
authors.lastname: Chevalier
authors.affiliation: Institut des Sciences Moléculaires d'Orsay, CNRS UMR 8214, Université Paris-Sud, 91405 Orsay, France.
authors.forename: R
authors.initials: R
authors.lastname: Thon
authors.affiliation: DSM/IRAMIS/SIS2M (CEA-CNRS UMR3299), Commissariat à l'Énergie Atomique, 91191 Gif-sur-Yvette, France.
authors.forename: R
authors.initials: R
authors.lastname: Pollet
authors.affiliation: Department of General Physics and Spectroscopy, Vilnius University, 01315 Vilnius, Lithuania.
authors.forename: J
authors.initials: J
authors.lastname: Ceponkus
authors.affiliation: Institut des Sciences Moléculaires d'Orsay, CNRS UMR 8214, Université Paris-Sud, 91405 Orsay, France.
authors.forename: C
authors.initials: C
authors.lastname: Crépin