Abstract
The energy levels for the hindered rotation of symmetric top molecules or ions in trigonal crystalline fields have been computed. The symmetry group of the Hamiltonian is C̄3v×C3 , where C̄3v is the trigonal group of rotations about the body-fixed axes and C3 is the trigonal group of rotations about the space-fixed axes. The tunneling frequencies of CH3D on a Vulcan III powdered sample have been computed and compared to the observed results.