文摘
Following photodissociation of gaseous acryloyl chloride, CH2CHC(O)Cl, at 193 nm, temporally resolved vibration鈥搑otational emission spectra of HCl (v 鈮?7, J 鈮?35) in region 2350鈥?250 cm鈥? and of CO (v 鈮?4, J 鈮?67) in region 1865鈥?300 cm鈥? were recorded with a step-scan Fourier-transform spectrometer. The HCl emission shows a minor low-J component for v 鈮?4 with average rotational energy Erot = 9 卤 3 kJ mol鈥? and vibrational energy Evib = 28 卤 7 kJ mol鈥? and a major high-J component for v 鈮?7 with average rotational energy Erot = 36 卤 6 kJ mol鈥? and vibrational energy Evib = 49 卤 9 kJ mol鈥?; the branching ratio of these two channels is 鈭?.2:0.8. Using electronic structure calculations to characterize the transition states and each intrinsic reaction coordinate, we find that the minor pathway corresponds to the four-center HCl-elimination of CH2ClCHCO following a 1,3-Cl-shift of CH2CHC(O)Cl, whereas the major pathway corresponds to the direct four-center HCl-elimination of CH2CHC(O)Cl. Although several channels are expected for CO produced from the secondary dissociation of C2H3CO and H2C鈺怌鈺怌鈺怬, each produced from two possible dissociation channels of CH2CHC(O)Cl, the CO emission shows a near-Boltzmann rotational distribution with average rotational energy Erot = 21 卤 4 kJ mol鈥? and average vibrational energy Evib = 10 卤 4 kJ mol鈥?. Consideration of the branching fractions suggests that the CO observed with greater vibrational excitation might result from secondary decomposition of H2C鈺怌鈺怌鈺怬 that was produced via the minor low-J HCl-elimination channel, while the internal state distributions of CO produced from the other three channels are indistinguishable. We also introduce a method for choosing the correct point along the intrinsic reaction coordinate for a roaming HCl elimination channel to generate a Franck鈥揅ondon prediction for the HCl vibrational energy.