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Global Analysis of a-, b- and c-Type Transitions Involving Tunneling Components of K = 0 and 1 States of the Methanol Dimer



C Lugez, Francis J. Lovas, Jon T. Hougen, N Ohashi


Spectral data on K = 0 and 1 levels of the methanol dimer available from previous and present Fourier transform microwave measurements have been interpreted globally, using a group-theoretically derived effective Hamiltonian and corresponding tunneling matrix elements to describe the splittings arising from a large number of tunneling motions. In the present work, 302 new measurements (40 K = 1 - 1 and 262 K = 1 - 0 transitions) were added to the previous data set to give a total of 584 assigned transitions with J-4, the lone-pair-exchange tunneling splittings were obtained experimentally. Matrix element expansions in J (J+l) used in the previous K=0 formalism. To reduce the number of adjustable parameters to an acceptable level in both the K = 0 and K = 1 effective Hamiltonians (used in separate K = 0 and K = 1 least-squares fits), a rather large number of assumptions concerning probably negligible parameters had to be made. The present fittings results should thus be considered as providing assurance of the group-theoretical line assignments as well as a nearly quantitative global interpretation of the tunneling splittings, even though they do not yet unambiguously determine the relative contributions from all 25 group-theoretically inequivalent tunneling motions in this complex, nor do they permit quantitative extrapolation to higher K levels.
Journal of Molecular Spectroscopy


Fourier transform microwave, hydrogen bonding, methanol dimer, microwave spectroscopy, multidimensional tunneling, rotational analysis, tunneling splittings


Lugez, C. , Lovas, F. , Hougen, J. and Ohashi, N. (1999), Global Analysis of a-, b- and c-Type Transitions Involving Tunneling Components of K = 0 and 1 States of the Methanol Dimer, Journal of Molecular Spectroscopy (Accessed December 10, 2023)
Created January 1, 1999, Updated February 17, 2017