Predissociative levels of CH B{sup 2}{Sigma}{sup -} state observed by 2-color laser-induced grating technique
- National Tsing Hua Univ., Hsinchu (Taiwan, Province of China)
Trace amount of CH in an acetylene flame was detected by resonance 4-wave mixing/2-color laser-induced grating spectroscopy (LIGS). Selected vibronic lines were detected either by probing the A {sup 2}{Delta} - X {sup 2}{Pi} transition in the 419-430 nm region with a grating formed from B {sup 2}{Sigma}{sup {minus}} - X {sup 2}{Pi} transition in the 387-396 nm region or by probing the B-X transition with a grating formed from the A-X transition. The double-resonance nature of this technique is advantageous in marking the specific state and obtaining unambiguous assignments. Furthermore, predissociative states with small yield of fluorescence (hence unobservble by the laser-induced fluorescence technique) can be readily detected with LIGS. The predissociative levels of the B state were detected by means of the former scheme with grating formed from the B-X transition; lines up to N{prime} = 21 of v{prime} = 0 were observed. The line position and the linewidth (hence the lifetime) of these previously unobserved predissociative levels were determined. At N{prime}=19 (v{prime}=0), linewidth broadening becomes apparent and the linewidth increases to {approximately}7 cm{sup -1} at N{prime}=21; a more accurate predissociation threshold was consequently determined.
- OSTI ID:
- 456885
- Report Number(s):
- CONF-9506113--
- Country of Publication:
- United States
- Language:
- English
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