NEAR-INFRARED ELECTRONIC TRANSIENT ABSORPTION SPECTRUM OF METHYLENE
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Date
1994
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Publisher
Ohio State University
Abstract
Methylene ($CH_{2}$) has been the subject of numerous studies since Herzberg and $Johns^{1}$ first analyzed the $\tilde{b}\leftarrow \tilde{a}$ electronic spectrum in 1966. The electronic spectrum of $CH_{2}$ is complicated by singlet-triplet interactions between the $\tilde{a},\tilde{ b}$, and $\widetilde{X}^{3}B^{1}$ states, the Renner-Teller Effect between the $\tilde{b}$ and $\tilde{a}$ states, which correlate with a degenerate $^{1}\Delta_{g}$ state at the linear configuration, and spin-orbit coupling. Recently, Green et $al.^{2}$ reported a theoretical investigation of the $CH_{2} \tilde{b} \leftarrow \tilde{a}$ electronic spectrum. In this study, they predicted the positions of many more vibronic bands than were observed by Herzberg and $Johns.^{1}$ Although the visible spectrum of $CH_{2}$ has been quire extensively studied, there are very few experiments in near-IR region due to less efficient dye laser operation at longer wavelengths. We have constructed a Ti:sapphire laser based transient absorption spectrometer and have measured the $CH_{2} \tilde{b} \leftarrow \tilde{a}$ electronic spectrum between 11400 and $12500 cm^{-1}$ at Doppler limited resolution. Our spectrum has indeed shown more lines than the previous $report.^{1}$ Furthermore, reassignments of several previously $observed^{1}$ bands suggested by Green et $al.^{2}$ have bee confirmed. The analysis is still in progress. The new experimental data nd current state of the analysis will be presented. Acknowledgment: This work w carried out under Contract No. DE-AC02-76CH00016 with the U. S. Department of Energy and supported by its Office of Basic Energy Science, Division of Chemical Sciences.
Description
1. G. Herzberg and J. W. C. Johns, Proc. Roy. Soc. A. 295, 107 (1966). 2. W. H. Green, JR., N. C. Handy, P. J. Knowles, S. Carter, J. Chem. Phys. 94, 118 (1991).
Author Institution: Department of Chemistry, Brookhaven National Laboratory
Author Institution: Department of Chemistry, Brookhaven National Laboratory