Gas-phase photodissociation of CH 3COCN at 308 nm by time-resolved Fourier-transform infrared emission spectroscopy
- Citation:
- Yeh, Y-Y, Chao M-H, Tsai P-Y, Chang Y-B, Tsai M-T, Lin K-C. 2012. Gas-phase photodissociation of CH 3COCN at 308 nm by time-resolved Fourier-transform infrared emission spectroscopy. Journal of Chemical Physics. 136, Number 4
Abstract:
By using time-resolved Fourier-transform infrared emission spectroscopy, the fragments of HCN(v 1, 2) and CO(v 1-3) are detected in one-photon dissociation of acetyl cyanide (CH 3COCN) at 308 nm. The S 1(A ″), 1(n O, π CO) state at 308 nm has a radiative lifetime of 0.46 ± 0.01 μs, long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of Ar collision-induced internal conversion is estimated to be (1-7) × 10 -12 cm 3 molecule -1 s -1. The measurements of O 2 dependence exclude the production possibility of these fragments via intersystem crossing. The high-resolution spectra of HCN and CO are analyzed to determine the ro-vibrational energy deposition of 81 ± 7 and 32 ± 3 kJmol, respectively. With the aid of ab initio calculations, a two-body dissociation on the energetic ground state is favored leading to HCN CH 2CO, in which the CH 2CO moiety may further undergo secondary dissociation to release CO. The production of CO 2 in the reaction with O 2 confirms existence of CH 2 and a secondary reaction product of CO. The HNC fragment is identified but cannot be assigned, as restricted to a poor signal-to-noise ratio. Because of insufficient excitation energy at 308 nm, the CN and CH 3 fragments that dominate the dissociation products at 193 nm are not detected. © 2012 American Institute of Physics.
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