Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

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 June 23, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 1, 1999, Updated February 17, 2017