RENNER-TELLER, SPIN ORBIT AND FERMI-RESONANCE INTERACTIONS IN X2-PI NCS INVESTIGATED BY LIF SPECTROSCOPY

被引:57
作者
NORTHRUP, FJ
SEARS, TJ
机构
[1] Department of Chemistry, Brookhaven National Laboratory, Upton, NY
关键词
D O I
10.1080/00268979000101631
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
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 and v3, 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 different v2 and K (= ∆ + I) 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 ε1 to 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 ε1 that agrees approximately with that determined from the vibronic-coupling parameter gK, assuming the same model for the interacting electronic states. © Taylor & Francis Ltd.
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页码:45 / 64
页数:20
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