Renner-Teller, spin-orbit and Fermi-resonance interactions in X2Π NCS investigated by LIF spectroscopy
作者:
F.J. Northrup,
TrevorJ. Sears,
期刊:
Molecular Physics
(Taylor Available online 1990)
卷期:
Volume 71,
issue 1
页码: 45-64
ISSN:0026-8976
年代: 1990
DOI:10.1080/00268979000101631
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The electronic spectrum of the NCS radical is obtained following UV excimer-laser photolysis of C2H5NCS in a large excess of inert gas in a supersonic free jet expansion. The spectrum is complicated by the presence of Renner-Teller and spin-orbit coupling and a Fermi resonance between the doubly excited bending vibration andv3, the CS stretching vibration. Bending vibronic level structure in the X2Π ground state of the radical is determined from a variety of laser-induced-fluorescence techniques, including stimulated-emission pumping. These energy levels are used to determine vibronic-coupling parameters for the radical. Coupling between close-lying bending levels with differentv2andK(= Λ +l) is found to be important because some of these levels are close together in NCS owing to the very large spin-orbit coupling. A parameter representing this effect is related to the dipolar contribution ε1to the Renner-Teller coupling parameter ε by applying perturbation theory to a simple model involving the X2Π and B2Σ+electronic states of NCS. This procedure results in an estimate for ε1that agrees approximately with that determined from the vibronic-coupling parametergK, assuming the same model for the interacting electronic states.
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