Near-infrared vibronic spectrum of the CH[sub 2] [ital [tilde b]] [sup 1][ital B][sub 1][l arrow][ital [tilde a]] [sup 1][ital A][sub 1] transition

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.468015· OSTI ID:7094987

Chang, B; Wu, M; Hall, G E; Sears, T J ^[1]

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1. Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

A Doppler-limited high resolution vibronic spectrum of the methylene (CH[sub 2]) [ital [tilde b]] [sup 1][ital B][sub 1][l arrow][ital [tilde a]] [sup 1][ital A][sub 1] transition in the near-infrared wavelength region has been obtained using transient absorption techniques. The radical was produced by 308 nm excimer laser photolysis of ketene (CH[sub 2]CO) in a flow system. The analysis of this spectrum confirms the reassignments of some previously observed bands as well as the presence of new vibronic bands predicted by a recent [ital ab] [ital initio] calculation [Green [ital et] [ital al]., J. Chem. Phys. [bold 94], 118 (1991)]. We also measured the Doppler broadened profiles of low-[ital J] rotational lines of CH[sub 2] under collisionless conditions. From the line profile analysis, we find that the 308 nm photolysis of ketene produces fragments with isotropic and uncorrelated velocity and angular momentum distributions. The Doppler profiles also provide a view of the coincident product state distributions. The measured Doppler profiles are consistent with a rotational distribution of CO produced in coincidence with low energy CH[sub 2] states given by statistical phase space theory. The vibrationally excited coincident CO appears, however, to be produced about 2--3 times more efficiently than is predicted by various statistical theories. A frequency modulation (FM) technique has been adopted to improve the sensitivity of the transient absorption experiment. There is a significant improvement in the observed signal to noise ratio of the CH[sub 2] spectrum over the dual beam method previously used.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7094987
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 101:11; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

664200* -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)
664400 -- Experimentally Derived Information on Atomic & Molecular Properties-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION SPECTRA
CHEMICAL REACTIONS
COUPLING
DECOMPOSITION
DOPPLER EFFECT
EFFICIENCY
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
EXCIMER LASERS
EXCITED STATES
FREQUENCY MODULATION
GAS LASERS
INFRARED RADIATION
INFRARED SPECTRA
KETENES
LASERS
METHYLENE RADICALS
MODULATION
NEAR INFRARED RADIATION
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONS
RADICALS
RESOLUTION
ROTATIONAL STATES
SPECTRA
SPECTRAL SHIFT