The effects of surface temperature on the gas-liquid interfacial reaction dynamics of O({sup 3}P)+squalane
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)
OH/OD product state distributions arising from the reaction of gas-phase O({sup 3}P) atoms at the surface of the liquid hydrocarbon squalane C{sub 30}H{sub 62}/C{sub 30}D{sub 62} have been measured. The O({sup 3}P) atoms were generated by 355 nm laser photolysis of NO{sub 2} at a low pressure above the continually refreshed liquid. It has been shown unambiguously that the hydroxyl radicals detected by laser-induced fluorescence originate from the squalane surface. The gas-phase OH/OD rotational populations are found to be partially sensitive to the liquid temperature, but do not adapt to it completely. In addition, rotational temperatures for OH/OD(v{sup '}=1) are consistently colder (by 34{+-}5 K) than those for OH/OD(v{sup '}=0). This is reminiscent of, but less pronounced than, a similar effect in the well-studied homogeneous gas-phase reaction of O({sup 3}P) with smaller hydrocarbons. We conclude that the rotational distributions are composed of two different components. One originates from a direct abstraction mechanism with product characteristics similar to those in the gas phase. The other is a trapping-desorption process yielding a thermal, Boltzmann-like distribution close to the surface temperature. This conclusion is consistent with that reached previously from independent measurements of OH product velocity distributions in complementary molecular-beam scattering experiments. It is further supported by the temporal profiles of OH/OD laser-induced fluorescence signals as a function of distance from the surface observed in the current experiments. The vibrational branching ratios for (v{sup '}=1)/(v{sup '}=0) for OH and OD have been found to be (0.07{+-}0.02) and (0.30{+-}0.10), respectively. The detection of vibrationally excited hydroxyl radicals suggests that secondary and/or tertiary hydrogen atoms may be accessible to the attacking oxygen atoms.
- OSTI ID:
- 20662249
- Journal Information:
- Journal of Chemical Physics, Vol. 122, Issue 2; Other Information: DOI: 10.1063/1.1835268; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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