Photofragmentation of nitromethane in a molecular beam at 193 nm
We report the cross section for dissociation of nitromethane at 193 nm. It is (1.7 +- 1.0) x 10/sup -17/ cm/sup 2/ measured relative to that for H /sup 79/Br. From this, we infer that the quantum yield for the process is nearly unity. Photofragments of the dissociation were observed at masses 15, 16, and 30 corresponding to CH/sub 3/, O, and NO, but only a very small amount of fragments at mass 46 (NO/sub 2/) was measured. Time-of-flight spectra were obtained for all fragments except for mass 46. Our data is explained by assuming that two sequential absorptions of photons occur. The first photon dissociates CH/sub 3/NO/sub 2/ to CH/sub 3/ and NO/sub 2/. The second photon is absorbed by the NO/sub 2/ fragment to give NO+O. About 30% of the NO/sub 2/ participate in the second absorption and the rate determining step is the primary absorption. The primary absorption fragments are characterized by having a most probable kinetic energy of 7% of the maximum available energy with an average of 19%. The remainder of this energy appears as internal energy of the fragments which can include electronic excitation of NO/sub 2/ to the A /sup 2/B/sub 2/ state or even to further dissociation of NO/sub 2/ to NO+O.
- Research Organization:
- University of California, Los Alamos National Laboratory, Chemistry Division, Los Alamos, New Mexico 87545
- OSTI ID:
- 5960237
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 79:4; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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400500* -- Photochemistry
BEAMS
CHEMICAL EXPLOSIVES
CHEMICAL REACTIONS
CROSS SECTIONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
EXPLOSIVES
MASS SPECTROSCOPY
MOLECULAR BEAMS
NITRO COMPOUNDS
NITROMETHANE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONS
SPECTROSCOPY
ULTRAVIOLET RADIATION