Fourier Transform Microwave Spectroscopic Study of the CO–CH4 van der Waals Complex.
Yaqian Liu and Wolfgang Jäger
Department of Chemistry, University of Alberta, Edmonton AB T6G 2G2, Canada
Rotational spectra of various isotopomers of the CO–CH4 van der Waals complex were recorded using a pulsed molecular beam Fourier transform microwave spectrometer. Rotational transitions within three internal rotor states, namely the j=0, K=0; j=1, K=0; and j=2, K=1 states, were measured and assigned. The spectrum of the C17O–CH4 isotopomer showed nuclear quadrupole hyperfine structure. Rotational, centrifugal distortion, and nuclear quadrupole coupling constants were determined and were used to obtain structural parameters. The obtained ground state results were compared with those previously determined from the infrared and millimeter wave spectra.1 The j=1, K=0 levels were found to be Coriolis perturbed by nearby j=1, K=1 levels. The observed j=2, K=1 transitions are stronger than predicted from the spin statistical weight obtained from a molecular symmetry group analysis, which is attributed to a larger vibrationally averaged dipole moment in this internal rotor state compared to the other two states.
1 C. Xia, K. A. Walker, and A. R. W. McKellar, J. Chem. Phys. 114, 4824 (2001).