title: Solvent response to solute photo-dissociation.
abstract: Ultraviolet-visible and infrared transient-absorption spectroscopy are used to investigate the transfer of energy from nitrite to water during the photo-dissociation of NO2-(aq). Nitrite is dissociated by photo-excitation at 200 nm. About 40% of the photo-fragments recombine and relax on a 3 ps timescale, while diffusive recombination accounts for another 10% of the fragments during the subsequent 50 ps. The infrared transient-absorption spectra of the photo-dissociation of nitrite solvated in H2O and D2O show no evidence of excited vibrations after 0.5 ps. Instead they reveal a sub-0.5 ps change in the infrared absorption similar to what is observed when the temperature of water is increased. Since this spectral change is associated with the weakening of the hydrogen-bond network, we infer that excess energy from the dissociation of nitrite is dissipated to the local hydrogen-bonded water network in less than 0.5 ps. The rapid change in the infrared absorption is followed by a slower (50 ps) component associated with the energy dissipation to the solvent as the photo-fragments diffusively recombine and relax.
authors.affiliation: Department of Chemistry, University of Aarhus, Langelandsgade 140, DK- 8000, Aarhus, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Petersen
authors.forename: Jan
authors.initials: J
authors.lastname: Thøgersen
authors.forename: Svend
authors.initials: S
authors.lastname: Knak Jensen
authors.forename: Søren R
authors.initials: SR
authors.lastname: Keiding
authors.forename: Paola
authors.initials: P
authors.lastname: Sassi
mesh_terms: D017666:Deuterium Oxide / Q000737:chemistry* / Q000528:radiation effects*; D004735:Energy Transfer; D009573:Nitrites / Q000737:chemistry* / Q000528:radiation effects*; D010777:Photochemistry; D011789:Quantum Theory; D012995:Solubility; D012997:Solvents / Q000737:chemistry / Q000528:radiation effects; D013055:Spectrophotometry, Infrared / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013997:Time Factors; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D009573:Nitrites; D012997:Solvents; D014867:Water; D017666:Deuterium Oxide