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The effects of surface temperature on the gas-liquid interfacial reaction dynamics of O(³P)+squalane

  • OH/OD product state distributions arising from the reaction of gas-phase O(³P) atoms at the surface of the liquid hydrocarbon squalane C₃₀H₆₂/C₃₀D₆₂ have been measured. The O(³P) atoms were generated by 355 nm laser photolysis of NO₂ 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′=1) are consistently colder (by 34±5 K) than those for OH/OD(v′=0). This is reminiscent of, but less pronounced than, a similar effect in the well-studied homogeneous gas-phase reaction of O(³P) 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′=1)/(v′=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.

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    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 122, 024712 (2005) and may be found at https://doi.org/10.1063/1.1835268

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Author:Sven P. K. KöhlerORCiD, Mhairi Allan, Hailey Kelso, David A. Henderson, Kenneth G. McKendrick
DOI original:https://doi.org/10.1063/1.1835268
Parent Title (English):The Journal of Chemical Physics
Publisher:AIP Publishing
Document Type:Article
Year of Completion:2005
Publishing Institution:Hochschule Hannover
Release Date:2022/06/22
GND Keyword:Oberflächentemperatur; Reaktionsdynamik; Squalan; Laserphotolyse; Hydroxyl
Article Number:024712
Link to catalogue:1809791596
Institutes:Fakultät II - Maschinenbau und Bioverfahrenstechnik
DDC classes:660 Technische Chemie
Licence (German):License LogoUrheberrechtlich geschützt