Complete characterization of the (D2O)2 ground state: high Ka rotation-tunneling levels.

We report the observation of extensive a- and c-type rotation-tunneling (RT) spectra of (D2O)2 for Ka = 0-4. These data allow quantification of molecular constants and tunneling splittings for a number of previously unobserved RT states of (D2O)2. The vibrational ground state has thus been characterized to energies as high as those of some of the intermolecular vibrations, and we present the first test of the VRT(ASP-W) potential at these high Ka states.

The Ground and First Excited Torsional States of Acetic Acid.

A global fit of microwave and millimeter-wave rotational transitions in the ground and first excited torsional states (v(t) = 0 and 1) of acetic acid (CH(3)COOH) is reported, which combines older measurements from the literature with new measurements from Kharkov, Lille, and NIST. The fit uses a model developed initially for acetaldehyde and methanol-type internal rotor molecules. It requires 34 parameters to achieve a unitless weighted standard deviation of 0.84 for a total of 2518 data and includes A- and E-species transitions with J