OBSERVATION OF $(H_{2}O)_{2}$ K-1 TRANSITIONS OF E SYMMETRY AND DISCUSSION OF NUCLEAR HYPERFINE SPLITTINGS

Abstract

We have recently observed a.type microwave and radiofrequency spectra from K-1 levels of E symmetry for $(H_{2}O)_{2}$. As anticipated from group theoretical arguments and similar to K-O E.type spectra which we observed earlier, these transitions do not exhibit the tunneling doubling found in the a-type spectra for nondegenerate tunneling levels. Rotational constants and K-type doublings were determined from several transitions of low J. which were obtained by molecular beam electric resonance spectroscopy. The relatively strong intensity of these lines correlates with the K-O E states lower in energy with respect to the proton acceptor $180^{\circ}$ rotation tunneling motion. The large K-doubling, which is 259.92 MHz for the J-1 state, is also in reasonable agreement with a prediction by L.H. Coudert and J.T. Hougen for these levels. Nuclear hyperfine splittings were observed for these transitions, in addition to those for the K-O states of E symmetry. These splittings will be discussed in terms of the proton spin-spin interaction and the structure of the diner.