CH3 state distributions form the reactions of O(1D) with saturated and chlorinated hydrocarbons

Imaging CH3SH photodissociation at 204 nm: the SH + CH3 channel

The SH + CH(3) product channel for the photodissociation of CH(3)SH at 204 nm was investigated using the sliced velocity map ion imaging technique with the detection of CH(3) products using state selective (2+1) resonance enhanced multiphoton ionization (REMPI). Images were measured for CH(3) formed in the ground and excited vibrational states (v(2) = 0, 1, and 2) of the umbrella mode from which the correlated SH vibrational state distributions were determined. The vibrational distribution of the SH fragment in the SH + CH(3) channel at 204 nm is clearly inverted and peaks at v = 1. The highly negative anisotropy parameter of the CH(3) (v(2) = 0, 1, and 2) products is indicative of a fast dissociation process for C-S bond cleavage. Two kinds of slower CH(3) products were also observed (one of which was partly vibrationally resolved) that are assigned to a two-step photodissociation processes, in which the first step is the production of the CH(3)S (X(2)E) radical via cleavage of the S-H bond in CH(3)SH, followed by probe laser photodissociation of nascent CH(3)S radicals yielding CH(3)(X(2)A(1), v(2) = 0-2) + S((3)P(j)/(1)D) products.

Multiple channel dynamics in the O(1D) reaction with alkanes

In this article, we briefly review the recent experimental studies of the multiple channel dynamics of the O((1)D) reaction with alkane molecules using the significantly improved universal crossed molecular beam technique. In these reactions, the dominant reaction mechanism is found to be an O atom insertion into the C-H bond, while a direct abstraction mechanism is also present in the OH formation channel. While the reaction mechanism is similar for all of these reactions, the product channels are quite different because of the significantly different energetics of these reaction channels. In the O((1)D) reaction with methane, OH formation is the dominant process while H atom formation is also a significant process. In the O((1)D) reaction with ethane, however, the CH(3) + CH(2)OH is the most important process, OH formation is still significant and H atom formation is of minor importance. A new type of O atom insertion mechanism (insertion into a C-C bond) is also inferred from the O((1)D) reaction with cyclopropane. Through these comprehensive studies, complete dynamical pictures of many multiple channel chemical reactions could be obtained. Such detailed studies could provide a unique bridge between dynamics and kinetics research.