METHANOL DIMER - THE EXPERIMENTAL RESULTS ON THE $\Delta K = 1$ SPECTRUM AND CONSISTENT ASSIGNMENTS OF K = 0 AND K = 1
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Date
1995
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Ohio State University
Abstract
Previously at this meeting we reported on the K = 0 spectrum of methanol $dimer^{1}$. In essence the theoretical model of Ohashi and $Hougen^{2}$ indicates that 16 tunneling-rotational states should occur for each rigid rotor rotational level; 4 nondegenerate A levels, 4 fourfold degenerate G levels, and 8 doubly degenerate E levels. The internal motions which give rise to these tunneling states are: methyl internal rotation of two inequivalent tops, hydrogen bond interchange between donor and acceptor sub-units, and interchange of the lone-pair orbital of the acceptor oxygen atom. Two years ago we reported observation of 15 of the expected 16 states for $K_{a} = 0$ manifold and intensity measurements showed one transition in the E state appears to be a degenerate pair since it is twice the twice the intensity of the other E state lines. Based on a two-top $model^{3}$ for the internal rotation splittings from the two inequivalent methyl groups, we searched for b-and c-type transitions with $\Delta K = 1$ in order to aid the assignment of the $K_{a} = 1$ manifold observed previously. Three and four level connections (loops) of K = 0 and $K_{a} = 1$ have been obtained for the four A states, four G states and four of the eight E states. The assignments and analysis with the two-top approach will be described.
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1. F. J. Lovas, R. D. Suenram, M. Yu. Tretyakov, S. P. Belov, and W. Stahl, 48th OSU Int. Symp. of Mol. Spectrosc. paper TC05. 2. N. Ohashi and J. T. Hougen, J. Mol. Spectrosc. 163, 86 (1994). 3. F. J. Lovas, S. P. Belov, M. Yu. Tretyakov, W. Stahl, and R. D. Suenram, J. Mol. Spectrosc. 170, in press (1995).
Author Institution: National Institute of Standards and Technology, Gaithersburg, MD 20899.; Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany.
Author Institution: National Institute of Standards and Technology, Gaithersburg, MD 20899.; Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany.