The reaction between O((1)D) and C(6)H(6) (or C(6)D(6)) was investigated with crossed-molecular-beam reactive scattering and time-resolved Fourier-transform infrared spectroscopy. From the crossed-molecular-beam experiments, four product channels were identified. The major channel is the formation of three fragments CO+C(5)H(5)+H; the channels for formation of C(5)H(6)+CO and C(6)H(5)O+H from O((1)D)+C(6)H(6) and OD+C(6)D(5) from O((1)D)+C(6)D(6) are minor. The angular distributions for the formation of CO and H indicate a mechanism involving a long-lived collision complex. Rotationally resolved infrared emission spectra of CO (12.9 for O((1)D)+C(6)D(6) is consistent with the expectation for an abstraction reaction. The mechanism of the reaction may be understood from considering the energetics of the intermediate species and transition states calculated at the G2M(CC5) level of theory for the O((1)D)+C(6)H(6) reaction. The experimentally observed branching ratios and deuterium isotope effect are consistent with those predicted from calculations.

Irradiation of samples of solid Ne near 3.0 K containing ethene (C(2)H(4)) with vacuum ultraviolet radiation at 120 nm from synchrotron yielded new spectral lines at 3141.0, 2953.6, 2911.5, 1357.4, 677.1, 895.3, and 857.0 cm(-1). These features are assigned to alpha-CH stretching (nu(1)), CH(2) antisymmetric stretching (nu(2)), CH(2) symmetric stretching (nu(3)), CH(2)-bending (nu(5)), HCCH cis bending (nu(7)), CH(2) out-of-plane bending (nu(8)), and alpha-CH out-of-plane bending (nu(9)) modes of C(2)H(3), respectively, based on results of (13)C- and D-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP and PW91PW91/aug-cc-pVTZ) predict vibrational wavenumbers, IR intensities, and isotopic ratios of vinyl radical that agree satisfactorily with our experimental results.

Following the photodissociation of o-fluorotoluene [o-C(6)H(4)(CH(3))F] at 193 nm, rotationally resolved emission spectra of HF(1< or =v< or =4) in the spectral region of 2800-4000 cm(-1) are detected with a step-scan Fourier transform spectrometer. HF(v< or =4) shows nearly Boltzmann-type rotational distributions corresponding to a temperature approximately 1080 K; a short extrapolation from data in the period of 0.5-4.5 mus leads to a nascent rotational temperature of 1130+/-100 K with an average rotational energy of 9+/-2 kJ mol(-1). The observed vibrational distribution of (v=1):(v=2):(v=3)=67.6: 23.2: 9.2 corresponds to a vibrational temperature of 5330+/-270 K. An average vibrational energy of 25+/-(3) (12) kJ mol(-1) is derived based on the observed population of HF(1< or =v< or =3) and estimates of the population of HF (v=0 and 4) by extrapolation. Experiments performed on p-fluorotoluene [p-C(6)H(4)(CH(3))F] yielded similar results with an average rotational energy of 9+/-2 kJ mol(-1) and vibrational energy of 26+/-(3) (12) kJ mol(-1) for HF. The observed distributions of internal energy of HF in both cases are consistent with that expected for four-center elimination. A modified impulse model taking into account geometries and displacement vectors of transition states during bond breaking predicts satisfactorily the rotational excitation of HF. An observed vibrational energy of HF produced from fluorotoluene slightly smaller than that from fluorobenzene might indicate the involvement of seven-membered-ring isomers upon photolysis.

Photolysis of methane dispersed (1/1000) in solid Ne at 3 K with vacuum-ultraviolet light from a synchrotron produced infrared absorption lines of several products, including new lines at 3319.3 and 1955.5 cm −1. Based on experiments with isotopic labeling and results of quantum-chemical calculations, these lines are assigned to the C-H stretching and C=C stretching modes, respectively, of interstellar molecule linear C 5 H radicals.