Knowledge Bank

R- and Q-branch rotational transitions of ortho- and meta-benzene-d, have been assigned over the 8-18 GHz range. Rotational constants and centrifugal distortion constants were fitted to the measured transition frequencies. The coordinates of the hydrogen nucleus were calculated in different ways from moments of inertia and their differences with respect to parent and monodeuterated species. The individual results are affected differently by zero-point vibrational effects. The deuterium quadrupole splitting of the $101-000$ transition at 8073 MHz has been resolved. The measured coupling constant is compard to results from NMR measurements in nematic solvents and to results from ab initio calculations.