A laser photolysis/time-resolved Fourier transform infrared emission study of OH(X 2Π,v) produced in the reaction of alkyl radicals with O(3P)

Abstract

The emission spectra of vibrationally excited hydroxyl radical products formed in the reactions of alkyl radicals with O(3P) atoms are detected using a laser photolysis/time-resolved Fourier transform infrared spectroscopy technique. For the reaction between oxygen atoms and ethyl, the radicals are produced simultaneously by the 193 nm photolysis of the precursors SO2 and diethyl ketone, respectively. The observed initial OH(v) product vibrational state distribution for the C2H5+O(3P) reaction is 0.18±0.03, 0.23±0.04, 0.29±0.05, 0.23±0.07, and 0.07±0.04 for v=1 to 5, respectively. The population inversion is best explained by a direct abstraction mechanism for this radical–radical reaction. Vibrationally excited hydroxyl radicals are also observed in the O+ethyl, O+n-propyl, and O+i-propyl reactions when using alkyl iodides as precursors of the alkyl radicals, although quantitative detail is not obtained due to competing reaction processes.

Reactions of oxygen atoms with hydrocarbon radicals: a priori kinetic predictions for the CH3+ O, C2H5+ O, and C2H3+ O reactions

“…As with most other radical + O reactions, only a few limited studies of the rate coefficients for the C 2 H 5 + O and C 2 H 3 + O reactions have been presented [19][20][21]. There have also been a few experimental and theoretical studies of the product distributions for these reactions [20][21][22][23][24][25]. The present theoretical predictions for the reaction rates provide useful new kinetic data for combustion modeling.…”

Photodissociation Dynamics of the Ethoxy Radical Investigated by Photofragment Coincidence Imaging

“…Hoyermann et al did find significant production of OH + C 2 H 4 , along with CH 3 + H 2 CO and H + CH 3 CHO. However, since an inverted vibrational distribution had been found for OH formed in this reaction, 19 they attributed this channel to direct bimolecular abstraction, rather than formation and subsequent isomerization of ethoxy to CH 2 CH 2 OH followed by dissociation. This conclusion, if correct, indicates that high internal energy on the ground state of ethoxy does not, by itself, lead to significant dissociation to OH + C 2 H 4 .…”

“…2,18 The reaction of O( 3 P) with ethyl radical, which can lead to the formation of the ethoxy radical with a great deal of excess energy, has been the subject of several experimental studies. [2][3][4]18,19 The fragmentation of chemically activated ethoxy radical formed in the reactions of ethyl radical with O, O 3 , and NO 3 was compared, 2 and it was found that both CH 3 + CH 2 O and H + CH 3 CHO were formed in all cases. The internal energy of the ethoxy radical formed in these reactions was peaked at roughly 4.0, 2.5, and 1.5 eV, respectively.…”

“…A study of the OH vibrational energy distribution in OH generated in the reaction of O( 3 P) and ethyl radical supported the conclusion that these products were formed by direct abstraction. 19 Spectroscopic studies have yielded information relevant to the ground and excited states of ethoxy. Foster et al, 20 on the basis of the rotational structure of the laser excitation spectrum, found the symmetry of the ground electronic state to be 2 A′′.…”

Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

“…They improved the signal-to-noise ratio by pulse-to-pulse normalization through detection of the total infrared fluorescence produced on each laser pulse. The system has been applied to studies of the OH emission in the X 2 P (v < 5) states [11] and NH 2 emission in the à state [12].…”