Spectroscopic studies of the {tilde B}{sup 2}A{sup {prime}{prime}}-{tilde X}{sup 2}A{sup {prime}{prime}} system of the jet-cooled vinoxy radical

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.474091· OSTI ID:508958

Brock, L R; Rohlfing, E A ^[1]

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1. Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 (United States)

We apply several techniques to the study of the {tilde B}{sup 2}A{sup {prime}{prime}}-{tilde X}{sup 2}A{sup {prime}{prime}} band system of the jet-cooled vinoxy radical, CH{sub 2}CHO. Vibronically resolved excitation spectra are obtained using both laser-induced fluorescence (LIF) and a two-color resonant four-wave mixing (TC-RFWM) scheme that provides the nonlinear equivalent of hole-burning spectra. Rotationally resolved LIF spectra recorded at low temperatures ({le}3K) provide rotational constants for 9 {tilde B}-state levels. We also measure the fluorescence lifetimes of 19 {tilde B}-state levels and obtain high-quality dispersed fluorescence (DF) spectra from seven of the most strongly fluorescing levels in the {tilde B} state. The excitation and DF spectra reveal far more vibrational levels in the two electronic states than have been previously observed. In total, we provide assignments for 54 levels observed in the first 3650cm{sup {minus}1} of the {tilde B} state and for 57 levels in the first 3100cm{sup {minus}1} of the {tilde X} state. These assignments include the identification of the a{prime} fundamentals for {nu}{sub 4} through {nu}{sub 9} and all three a{sup {prime}{prime}} overtones, 2{nu}{sub 10} through 2{nu}{sub 12}, in both states. The differences between the TC-RFWM and LIF spectra and the measured lifetimes indicate a dramatic increase in the predissociation rate of the {tilde B} state beginning at 1190cm{sup {minus}1} above the origin. The predissociation rate is markedly mode-specific and is enhanced by out-of-plane excitation, possibly due to vibronic coupling with either the {tilde A}{sup 2}A{prime} or {tilde C}{sup 2}A{prime} electronic states. The congestion and complexity of the DF spectra at high energies provides direct evidence of extensive intramolecular vibrational redistribution on the ground-state potential surface. {copyright} {ital 1997 American Institute of Physics.}

• OSTI ID: 508958
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 24 Vol. 106; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ABSORPTION SPECTRA
ATMOSPHERIC CHEMISTRY
COMBUSTION PRODUCTS
COOLING
ELECTRONIC STRUCTURE
FLUORESCENCE
HYDROCARBONS
JETS
POTENTIALS
PREDISSOCIATION
RADICALS
ROTATIONAL STATES
VIBRATIONAL STATES