The reaction products of the 193 nm photolysis of vinyl bromide and vinyl chloride studied by time-resolved Fourier transform infrared emission spectroscopy

Abstract

Time-resolved Fourier transform infrared (TRFTIR) emission spectroscopy has been used to study the 193 nm photolysis of vinyl bromide (C(2)H(3)Br) and vinyl chloride (C(2)H(3)Cl). Time-resolved IR emission was analysed to obtain nascent vibrational state populations of two primary photolysis products: HBr (v = 1-7) and HCl (v = 1-6). In both cases the nascent vibrational state populations monotonically decrease with increasing v and are in excellent agreement with previously published data. Time-resolved populations were analysed to yield rate constants for vibrational relaxation of HBr (v = 1-3) and HCl (v = 1-4) by parent vinyl bromide and vinyl chloride, respectively. In both cases the rate constants were found to increase with increasing vibrational quantum number, in agreement with a single quantum de-excitation via vibrational to vibrational energy transfer. Butadiene (C(4)H(6)) was identified as a secondary product of the photolysis of both vinyl halides, and shown to be formed from the reaction of parent vinyl halide with the vinyl radical. The presence of a buffer gas was found to produce a strong emission feature centred at 2,200 cm(-1), the intensity of which was dependent on the pressure of the buffer gas used, and whose kinetics are indicative of a secondary reaction product. We propose that this emission is from the vibrational progression of the electronic transition A(0, v, 1) --> X(0, v, 2) in the secondary reaction product C(2)H, whose formation route is favoured by the presence of buffer gas.

Ab initio large-amplitude quantum-tunneling dynamics in vinyl radical: a vibrationally adiabatic approach

“…8,15 More recently these efforts have been supplemented with cavity ring down techniques, by Fahr et al 7 in the near-UV as well as Pibel et al 12 in the visible region, which now permit even more sensitive time-resolved chemical-kinetic studies of vinyl species. Recent broadband detection of vinyl radical by time-resolved FTIR emission studies has also been demonstrated by Letendre et al 11 and Carvalho et al, 20 though still at a spectral resolution unable to address issues of large-amplitude H atom migration.…”

An ab initio study of the photodissociation of the vinyl radical

“…Several experimental studies have reported measurements of absorption bands to different electronic states of the VR in the last few decades. 11,[13][14][15][16][17][18][19][20] However, much of the experimental work has dealt with rovibrational spectroscopy of the double well and the tunneling dynamics of the VR in the ground X ˜2A 0 electronic state through the lowest-lying transition state. In this sense, infrared spectra [21][22][23] and tunneling splittings of the VR have been reported.…”

FTIR and Raman Spectroscopy Study of Soot Deposits Produced in the Infrared Multiphoton Dissociation of Vinyl Bromide

“…e transitions of vibrationally excited hydrogen bromide HBr (1-3) have been attributed to the bands occurring between 2,400 cm -1 and 2,700 cm −1 [61,62,64]. Furthermore, a solid deposit has been seen clinging to the cell walls and windows.…”