Grecea Mihail L, Backus Ellen H G, Kleyn Aart W, Bonn Mischa
Leiden Institute of Chemistry, University of Leiden, Einsteinweg 55, P. O. Box 9502, 2300 RA Leiden, The Netherlands.
J Phys Chem B. 2005 Sep 22;109(37):17574-8. doi: 10.1021/jp052586n.
The 266 nm photodissociation of bromoform adsorbed on an amorphous solid water (ASW) layer has been investigated for the first time under well-defined ultrahigh vacuum conditions. Time-of-flight (TOF) measurements indicate direct release of gas-phase Br, CHBr2, Br2, and CHBr species, with potential implications for stratospheric chemistry. Furthermore, new, ice-surface-mediated C-C (C2H2Br2) and C-O (CHBrO, CO) species are revealed in postirradiation temperature programmed desorption (TPD) and reflection absorption infrared (RAIR) spectra. A cross section of approximately 5 x 10(-20) cm2 is determined for bromoform photodissociation at 266 nm based on the integrated area of both the TOF spectra of Br and Br2 and the postirradiation TPD curves of CHBr3. The involvement of the free, non-hydrogen-bonded water groups at the ASW surface in the formation of the photoproducts is evident from the RAIRS results.
首次在明确的超高真空条件下研究了吸附在非晶态固态水（ASW）层上的溴仿的266纳米光解离。飞行时间（TOF）测量表明气相Br、CHBr2、Br2和CHBr物种直接释放，这对平流层化学有潜在影响。此外，在辐照后程序升温脱附（TPD）和反射吸收红外（RAIR）光谱中发现了新的、冰表面介导的C-C（C2H2Br2）和C-O（CHBrO、CO）物种。基于Br和Br2的TOF光谱的积分面积以及CHBr3的辐照后TPD曲线，确定了266纳米处溴仿光解离的截面约为5×10^(-20)平方厘米。RAIRS结果表明，ASW表面游离的、非氢键结合的水基团参与了光产物的形成。
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