ANALYSIS OF THE MICROWAVE AND FAR INFRARED-SPECTRUM OF THE WATER DIMER

The radiofrequency, microwave, and far infrared spectrum of the water dimer has been analyzed using an IAM-like treatment developed in two previous papers and slightly extended here. It was assumed for this analysis that four large amplitude motions are feasible in the water dimer, two of them being interconversion motions during which the hydrogen-bond acceptor monomer becomes the donor monomer and vice versa. The present global analysis of 173 transitions made possible the determination of 22 parameters in the theoretical formalism corresponding to the various tunneling motions, including the angles describing the J and K dependence of the tunneling splittings. In addition, the seven asymmetric rotor parameters A, B, C, DJ, DJK, d1, and d2 were determined, corresponding to constants with contributions from the various tunneling motions removed. These constants yielded a B-C value of 29.0 MHz and a b axis perpendicular to the plane of symmetry of the dimer. The effects of the tunneling motions on the origin of the anomalously large asymmetry splittings, as well as on the Coriolis coupling between K = 0 and K = 1 levels are also discussed. © 1990.