TUNNELING-ROTATION SPECTRUM OF THE HYDROGEN-FLUORIDE DIMER

The tunneling-rotation spectrum of the ground state of the hydrogen fluoride dimer, HF⋯HF, has been extended to the submillimeter wavelength region with the RAD-3 submillimeter spectrometer at Gorky in the frequency range 180-380 GHz at 210 K and pressures from 0.5 to 1.5 Torr. The spectrum has been reinvestigated at lower frequencies with a conventional Stark spectrometer at pressures between 0.1 to 0.2 Torr at the National Institute of Standards and Technology. Lines of the a-type K = 3 subband have been observed for the first time. The tunneling frequency for the K = 3 state is 114 306.35(53) MHz. The rotational constants of this subband are somewhat anomalous as compared with those for the lower K sublevels. For example, the B rotational constant for the Bu state is larger than that for the Ag state, while for all the lower K sublevels the opposite is true. Higher-J R- and P-branch lines of the K = 0 through K = 2 subbands have been identified and improved rotational constants for these states have been obtained. An atlas of all a- and b-type far infrared and microwave ground state tunneling-rotation transitions for K up to 3 giving frequency, uncertainty, and relative intensity has been prepared. © 1990.