THE ONSET OF INTRAMOLECULAR VIBRATIONAL-ENERGY REDISTRIBUTION AND ITS INTERMEDIATE CASE - THE NU-1 AND 2-NU-1 MOLECULAR-BEAM, OPTOTHERMAL SPECTRA OF TRIFLUOROPROPYNE

被引:95
作者
PATE, BH
LEHMANN, KK
SCOLES, G
机构
[1] Department of Chemistry, Princeton University, Princeton
关键词
D O I
10.1063/1.460796
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
Using the optothermal method for molecular beam, infrared spectroscopy, we have measured both the fundamental and first overtone of the acetylenic C-H stretch in CF3 CCH. In the fundamental we observe a spectrum which shows only few perturbations. The majority of lines can be successfully fit to a model assuming an anharmonic coupling of the C-H stretch to a single, near-resonant background state with a coupling matrix element of 0.006 cm-1. We have observed other perturbations in this spectrum, including a state coupled by a weak perpendicular Coriolis interaction. All observed couplings are very weak and local in nature. In the overtone, where the density of background states increases by a factor of 100, we observe a spectrum characteristic of a system in the intermediate case of IVR (intramolecular vibrational energy redistribution). Analysis of the R(0) and P(1) transitions provides a homogeneous IVR lifetime of about 2 ns, which is long compared to lifetimes generally quoted for overtone vibrational relaxation. The root-mean-square coupling matrix element in the overtone is about 0.0008 cm-1. The higher J transitions in the overtone suggest that Coriolis interactions are present in the spectrum. The interpretation of these spectroscopic results in the context of IVR is discussed.
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页码:3891 / 3916
页数:26
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