Sub-Doppler spectroscopy of thioformaldehyde: Excited state perturbations and evidence for rotation-induced vibrational mixing in the ground state

Journal Article · Tue Nov 01 00:00:00 EST 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.468287· OSTI ID:7168904

Clouthier, D J ^[1]; Huang, G; Adam, A G; Merer, A J ^[2]

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1. Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)
2. Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1 (Canada)

High-resolution intracavity dye laser spectroscopy has been used to obtain sub-Doppler spectra of transitions to 350 rotational levels in the 4[sup 1][sub 0] band of the [ital [tilde A]] [sup 1][ital A][sub 2]--[ital [tilde X]] [sup 1][ital A][sub 1] electronic transition of thioformaldehyde. Ground state combination differences from the sub-Doppler spectra, combined with microwave and infrared data, have been used to improve the ground state rotational and centrifugal distortion constants of H[sub 2]CS. The upper state shows a remarkable number of perturbations. The largest of these are caused by nearby triplet levels, with matrix elements of 0.05--0.15 cm[sup [minus]1]. A particularly clear singlet--triplet avoided crossing in [ital K][sub [ital a]][sup [prime]] = 7 has been shown to be caused by interaction with the [ital F][sub 1] component of the 3[sup 1]6[sup 2] vibrational level of the [ital [tilde a]] [sup 3][ital A][sub 2] state. At least 53% of the [ital S][sub 1] levels show evidence of very small perturbations by high rovibronic levels of the ground state. The number of such perturbations is small at low [ital J], but increases rapidly beyond [ital J]=5 such that 40%--80% of the observed [ital S][sub 1] levels of any given [ital J] are perturbed by ground state levels. Model calculations show that the density and [ital J] dependence of the number of perturbed levels can be explained if there is extensive rotation-induced mixing of the vibrational levels in the ground state.

• DOE Contract Number: FG05-86ER13544
• OSTI ID: 7168904
• Journal Information: Journal of Chemical Physics; (United States), Vol. 101:9; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
FORMALDEHYDE
ELECTRON SPECTRA
ROTATIONAL STATES
THIOLS
DOPPLER EFFECT
DYE LASERS
EXCITED STATES
FREQUENCY MIXING
GROUND STATES
RESOLUTION
TRIPLETS
VIBRATIONAL STATES
ALDEHYDES
ENERGY LEVELS
LASERS
LIQUID LASERS
MULTIPLETS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
SPECTRA
664200* - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)