HYDROGEN MIGRATION TUNNELING EFFECTS IN THE INFRARED SPECTRUM OF PROTONATED ACETYLENE $C_{2}H_{3}^{+}$
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Date
1986
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Ohio State University
Abstract
The goal of the present work is to indicate what sorts of rotation-vibration spectra might be expected for protonated acetylene when the three protons in the molecule are allowed to interchange roles in a cyclic mannner by migrating around an elliptical orbit enclosing the two carbon atoms, as suggested by ab initio $calculations^{1,2}$. [FIGURE] On the one hand, approximate rotation-vibration-tunneling energy levels can be obtained by mapping the protonated acetylene problem onto an internal rotation problem already discussed in the $literature^{3}$ in terms of numerical calculations in a Principal-Axis-Method treatment. On the other hand, semi-quantitative rotation-vibration-tunneling energy levels can be obtained for the high barrier limit by applying to protonated acetylene an Internal-Axis-Method-like formalism originally set up to treat the water dimer. The agreement betwen the numerical PAM calculations and the algebraic IAM results serves as a check on both. Unfortunately, the development of this formalism, with its tunneling splittings, statistical weights, selection rules, etc., has not yet led to an assignment of the spectrum of $C_{2}H_{3}^{+}$ reported last year at this meeting by Crofton and $Oka^{4}$.
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$^{1}$ J. Weber, M. Yoshimine and A. D. McLean, J. Chem. Phys. 64, 4159-4164 (1976). 2 G. P. Raine and H. F. Schaefer III, J. Chem. Phys. 81, 4034-4037 (1984). 3 E. B. Wilson Jr., C. C. Lin and D. R. Lide, J. Chem. Phys. 23, 136-142 (1955). 4 M. W. Crofton and T. Oka, Columbus Symposium Abstracts 1985, TE13. Address of Hougen: Molecular Spectroscopy Division, National Bureau of Standards, Gaithersburg, MD 20899.
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