Photofragment imaging of methane
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 (United States)
- Department of Chemistry, Stanford University, Stanford, California 94305 (United States)
- Combustion Research Facility, Sandia National Laboratories, Livermore. , California 94551 (United States)
The photolysis of methane is studied using photofragment imaging techniques. Our study reveals that the photolysis of methane proceeds via many different pathways. The photofragment imaging technique is used to resolve and characterize these various pathways and provides therefore unique insight into the dynamical processes that govern this photodissociation. The formation of H-atom photofragments following absorption of a Lyman-{alpha} photon, and H{sub 2} photofragments following absorption of two ultraviolet photons ({lambda}=210{endash}230 nm) are studied. The measured H-atom photofragment images reveal that a channel that produces fast H atoms concomitant with methyl fragments is dominant in the Lyman-{alpha} photolysis of methane. This channel leads to an anisotropic recoil of the fragments. A secondary channel is observed leading to the formation of somewhat slower H atoms, but an unique identification of this second channel is not possible from the data. At least part of these slower H atoms are formed via a channel that produces H atoms concomitant with CH and H{sub 2} photofragments. The recoil of these slower H atoms appears to be isotropic. The measured, state-resolved H{sub 2}({ital v},{ital J}), photofragment images reveal that two channels lead to H{sub 2} photofragments from the two-photon photolysis of methane: a channel that leads to H{sub 2} products concomitant with methylene fragments; and a channel that leads to H{sub 2} products concomitant with CH and H fragments. H{sub 2}({ital v},{ital J}) rotational and vibrational distributions are measured for each of these two channels separately. The H{sub 2} products formed via the H{sub 2}+CH{sub 2} channel are rotationally and vibrationally highly excited, whereas those formed via the H{sub 2}+CH+H channel are rotationally and vibrationally cooler. Rotational distributions of H{sub 2} formed via the H{sub 2}+CH+H channel are well reproduced by Boltzmann distributions. (Abstract Truncated)
- OSTI ID:
- 283438
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 11 Vol. 104; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Photofragment imaging: The two-photon dissociation of methane
Investigation of acetyl chloride photodissociation by photofragment imaging