IDENTIFICATION OF TORSIONAL TRANSITIONS IN THE SUPERSONIC JET SPECTRUM OF MONO-METHYL TETRAZINE

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1984

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Ohio State University

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Identification of the strong torsional transitions, with $m^{\prime}=m^{\prime\prime}=\pm 1$ and delta m equal to zero, in the high-resolution laser excitation molecular beam spectrum of the methyl tetrazine 5613 {\AA} origin band recently published by Haynam and Levy (1) has been made. Use of their published tetrazine frame rotational constants with $A_{T} = 5.3403 cm^{-1}, \triangle A_{T} = -0.034 cm^{-1}$ results in predicting the positions of the torsional transitions for J up to 3 to within about $.001 cm^{-1}$ precision. However, line positions for larger values of J are not adequately calculated using these constants in the asymmetric top/free internal rotor model (2), the fit worstening with increasing J. Reasons for this discrepancy are discussed. Assumption of an equilibrium distribution over both rotation and torsion states for a specified temperature does not quantitatively reproduce the observed molecular beam spectrum intensities. However, a simple model based on a suggestion of Smalley, et al. (3) does produce the observed spectral intensities in at least the simplest of the Haynam and Levy (1) spectra. Indeed, this simple model, with $T_{rot} = 0.50K$ and $T_{m=1} = 5.0K$ reproduces the published 500 PSI backing-pressure spectrum on a line-for-line basis.

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1. C.A. Haynam and D.H. Levy, J. Phys. Chem. 87, 2091 (1983). 2. M.A. Leugers and C.J. Seliskar, J. Mol. Spectrosc. 91, 150-164 (1982). 3. S.M. Beck, M.G. Liverman, D.L. Monts and R.E. Smalley, J. Chem. Phys. 70, 232-237 (1979).
Author Institution: Department of Chemistry, University of Cincinnati

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