Time-resolved infrared absorption studies of the solvent-dependent vibrational relaxation dynamics of chlorine dioxide

Journal Article · Mon Aug 22 00:00:00 EDT 2005 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2000234· OSTI ID:20723036

Bolinger, Joshua C; Bixby, Teresa J; Reid, Philip J ^[1]

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1. Box 351700, Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States)

We report a series of time-resolved infrared absorption studies on chlorine dioxide (OClO) dissolved in H{sub 2}O, D{sub 2}O, and acetonitrile. Following the photoexcitation at 401 nm, the evolution in optical density for frequencies corresponding to asymmetric stretch of OClO is measured with a time resolution of 120{+-}50 fs. The experimentally determined optical-density evolution is compared with theoretical models of OClO vibrational relaxation derived from collisional models as well as classical molecular-dynamics (MD) studies. The vibrational relaxation rates in D{sub 2}O are reduced by a factor of 3 relative to H{sub 2}O consistent with the predictions of MD. This difference reflects modification of the frequency-dependent solvent-solute coupling accompanying isotopic substitution of the solvent. Also, the geminate-recombination quantum yield for the primary photofragments resulting in the reformation of ground-state OClO is reduced in D{sub 2}O relative to H{sub 2}O. It is proposed that this reduction reflects enhancement of the dissociation rate accompanying vibrational excitation along the asymmetric-stretch coordinate. In contrast to H{sub 2}O and D{sub 2}O, the vibrational-relaxation dynamics in acetonitrile are not well described by the theoretical models. Reproduction of the optical-density evolution in acetonitrile requires significant modification of the frequency-dependent solvent-solute coupling derived from MD. It is proposed that this modification reflects vibrational-energy transfer from the asymmetric stretch of OClO to the methyl rock of acetonitrile. In total, the results presented here provide a detailed description of the solvent-dependent geminate-recombination and vibrational-relaxation dynamics of OClO in solution.

• OSTI ID: 20723036
• Journal Information: Journal of Chemical Physics, Vol. 123, Issue 8; Other Information: DOI: 10.1063/1.2000234; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ACETONITRILE
CHLORINE
CHLORINE COMPOUNDS
COUPLING
GROUND STATES
HEAVY WATER
INFRARED SPECTRA
ISOTOPIC EXCHANGE
MOLECULAR DYNAMICS METHOD
OPACITY
PHOTON-MOLECULE COLLISIONS
REACTION KINETICS
RELAXATION
SOLUTIONS
SOLVENTS
TIME RESOLUTION
VIBRATIONAL STATES
WATER