Photodissociation of H sub 2 O sub 2 and CH sub 3 OOH at 248 nm and 298 K: Quantum yields for OH, O( sup 3 P ) and H( sup 2 S )

Journal Article · Mon Jan 15 04:00:00 EST 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.458081· OSTI ID:7028067

Vaghjiani, G L; Ravishankara, A R ^[1]

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1. Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado 80303 (USA) Department of Chemistry and Biochemistry Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309 (USA)

The quantum yields of the products, OH({ital X} {sup 2}{Pi}), O({sup 3}{ital P}) (plus O({sup 1}{ital D})) and H({sup 2}{ital S}), in the photolysis of H{sub 2}O{sub 2} and CH{sub 3}OOH at 248 nm and 298 K have been measured. OH was directly observed by laser-induced fluorescence while the atomic species were detected by cw-resonance fluorescence. All quantum yield measurements were made using relative methods. The quantum yields of OH, O, and H in H{sub 2}O{sub 2} photolysis were measured relative to the well known quantum yields of O({sup 1}{ital D}) and O({sup 3}{ital P}) in the photodissociation of O{sub 3}, and H({sup 2}{ital S}) in CH{sub 3}SH. The values we obtain are, 2.09{plus minus}0.36, {lt}0.002 and {lt}0.0002 for OH, O, and H, respectively. For CH{sub 3}OOH photolysis, the quantum yield of OH was measured relative to our value for OH quantum yield in H{sub 2}O{sub 2} photolysis, and the quantum yields of O and H relative to those in O{sub 3} and CH{sub 3}SH photodissociation, respectively. The values we obtain are, 1.00{plus minus}0.18, {lt}0.007 and 0.038{plus minus}0.007 for OH, O, and H, respectively. In both H{sub 2}O{sub 2} and CH{sub 3}OOH photolysis, the observed O and H quantum yields showed an apparent dependence on the fluence of the photolysis light, the possible origin of which is discussed. The large quantum yield of OH we measure is consistent with the known continuous and unstructured absorption spectra of these molecules in this wavelength region, where the most important process is the dissociative ({ital {tilde A}} {sup 1}{ital A}{l arrow}{ital {tilde X}}{sup 1}{ital A}) transition to give OH({ital X} {sup 2}{Pi}, {ital v}{double prime}=0) fragment.

• OSTI ID: 7028067
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 92:2; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

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