Highly predissociative levels of CH B2Σ- state detected with two-color resonant four-wave mixing spectroscopy

Awadhesh Kumar*, Chih Chang Hsiao, Wen Ching Hung, Yuan-Pern Lee

*Corresponding author for this work

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We demonstrate an application of two-color resonant four-wave mixing spectroscopy to detect highly predissociative levels of CH in the B2Σ- state in a hostile environment of an oxyacetylene flame. The probe and grating wavelengths are in resonance with the A2Δ-X2Π and B2Σ--X2Π systems, respectively. We measured 49 previously unobserved rovibronic lines of the 0-0 band and 38 additional lines of the 1-0 band of the B2Σ--X2Π system to access rotational quantum number N up to 21 and 13 of v=0 and 1 in the B2Σ- state, respectively. Inclusion of additional line positions measured for the 0-0 and the 1-0 bands yields spectral parameters of the B2Σ- state significantly improved over those obtained previously with only nonpredissociative lines; one additional centrifugal-distortion parameter Lv is evaluated significantly. Although power saturation is significant even at smallest practical laser energies, we estimated lifetimes through the power dependence of linewidths. The lifetimes of the highest measurable level of B2Σ- (v=0 and 1) are 3±1 (N=20) and 8±2 (N=11) ps, respectively.

Original languageEnglish
Pages (from-to)3824-3830
Number of pages7
JournalJournal of Chemical Physics
Issue number10
StatePublished - 1 Dec 1998

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