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題 名 | Product Imaging Studies of Photodissociation and Bimolecular Reaction Dynamics |
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作 者 | Houston,Paul L.; Cosofret,Bogdan R.; Dixit,Amitaviram; Dylewski,Scott M.; Geiser,Joseph D.; Mueller,Julie A.; Wilson,Ruth J.; Pisano,Patrick J.; Westley,Michael S.; Lorenz,K. Thomas; Chandler,David W.; | 書刊名 | Journal of the Chinese Chemical Society |
卷 期 | 48:3 2001.06[民90.06] |
頁 次 | 頁309-318 |
分類號 | 346.01 |
關鍵詞 | Photodissociation; Rotational energy transfer; Ozone; Sulfur dioxide; Nitric oxide; |
語 文 | 英文(English) |
英文摘要 | This paper briefly reviews recent progress in product imaging studies of photodissociation and bimolecular reaction dynamics. The SO2 + h�� �_ SO(3��-) + O(3P2) channel in the ultraviolet photodissociation of sulfur dioxide at photolysis wavelengths between 202 and 207 nm has been studied using resonance-enhanced multiphoton ionization with time-of-flight product imaging. These imaging experiments allowed the determination of the vibrational populations of the SO(3��-) fragment at several wavelengths. A change in the vibrational populations occurs from a distribution where most of the population is in v = 0 for wavelengths shorter than 203.0 nm to one where the population is more evenly distributed for longer wavelength dissociation. The changes in the internal energy distribution are attributed to participation of two different predissociation mechanisms. Our data suggest that the predissociation mechanism below 203.0 nm involves an avoided crossing with the repulsive singlet state 1A1. The O3(X1A1) + h�� �_ O(2p 3PJ) + O2(X 3�懲- ) product channel in the UV photodissociation of ozone has been investigated at photolysis wavelengths of 226, 230, 233, 234, 240, and 266 nm. At 226, 230, 233, 234, and 240 nm, the yield of the O2 product in vibrational states greater than or equal to 26 was 11.8 ± 1.9%, 11.5 ± 1.2%, 8.2 ± 2.0, 4.7 ± 1.8, and 0.6 ± 0.1%, respectively. Two-dimensional ion counting product imaging has also been used to determine the bond energy for the dissociation of jet-cooled O3 into O(1D) + O2(1��). The bond dissociation energy into O(1D) + O2(1D) was found to be 386.59 ± 0.04 kJ/mol. The standard heat of formation of O3 is calculated to be -144.31 ± 0.14 kJ/mol. State-selective differential cross sections for rotationally inelastic scattering of NO (Ji = 0.5, 1.5, F1 �_ Jf = 2.5-12.5, F1 and Jf =1.5-9.5, F2) from He and D2 measured by crossed molecular beam ion imaging are reported. The images typically exhibit a single broad rotational rainbow maximum that shifts from the forward to the backward scattering direction with increasing J. The angle of the rainbow maximum was lower at a given �寓 for D2 than for He as a collision partner. At a collision energy of ~500 cm-1, primarily the repulsive part of the potential surface is probed, which can be modeled with a 2-D hard ellipse potential. This model for rotationally inelastic scattering is shown to qualitatively match the experimental differential cross sections. A more advanced CEPA PES for NO + He does not give substantially better agreement with the experiment. |
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