Photolysis of pure solid O{sub 3} and O{sub 2} films at 193 nm

Journal Article · Sat May 21 00:00:00 EDT 2011 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3589201· OSTI ID:21560249

Raut, U; Loeffler, M J; Fama, M; Baragiola, R A ^[1]

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1. Laboratory of Atomic and Surface Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

We studied quantitatively the photochemistry of solid O{sub 3} and O{sub 2} films at 193 nm and 22 K with infrared spectroscopy and microgravimetry. Photolysis of pure ozone destroyed O{sub 3}, but a small amount of ozone remained in the film at high fluence. Photolysis of pure O{sub 2} produced O{sub 3} in an amount that increased with photon fluence to a stationary level. For both O{sub 2} and O{sub 3} films, the O{sub 3}:O{sub 2} ratio at large fluences is {approx}0.07, about two orders of magnitude larger than those obtained in gas phase photolysis. This enhancement is attributed to the increased photodissociation of O{sub 2} due to photoabsorption by O{sub 2} dimers, a process significant at solid-state densities. We obtain initial quantum yield for ozone synthesis from solid oxygen, {Phi}(O{sub 3}) = 0.24 {+-} 0.06, and quantum yields for destruction of O{sub 3} and O{sub 2} in their parent solids, {Phi}(-O{sub 3}) = 1.0 {+-} 0.2 and {Phi}(-O{sub 2}) = 0.36 {+-} 0.1. Combined with known photoabsorption cross sections, we estimate probabilities for geminate recombination of 0.5 {+-} 0.1 for O{sub 3} fragments and 0.88 {+-} 0.03 for oxygen atoms from O{sub 2} dissociation. Using a single parameter kinetic model, we deduce the ratio of reaction cross sections for an O atom with O{sub 2} vs. O{sub 3} to be 0.1-0.2. The general good agreement of the model with the data suggests the validity of the central assumption of efficient energy and spin relaxation of photofragments in the solid prior to their reactions with other species.

• OSTI ID: 21560249
• Journal Information: Journal of Chemical Physics, Vol. 134, Issue 19; Other Information: DOI: 10.1063/1.3589201; (c) 2011 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
ABSORPTION SPECTROSCOPY
ATOMS
CROSS SECTIONS
DIMERS
DISSOCIATION
FILMS
INFRARED SPECTRA
OXYGEN
OXYGEN COMPOUNDS
OZONE
PHOTOCHEMISTRY
PHOTOLYSIS
PHOTONS
PROBABILITY
REACTION KINETICS
RECOMBINATION
RELAXATION
SOLIDS
SYNTHESIS
BOSONS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELEMENTARY PARTICLES
ELEMENTS
KINETICS
MASSLESS PARTICLES
NONMETALS
PHOTOCHEMICAL REACTIONS
SPECTRA
SPECTROSCOPY