Torsional eneÅrgies and relative intensities of far-infrared transitions in the vibrational ground state of methanol-D2

Abstract In this paper, the pure torsional energies of asymmetrically deuterated methanol CHD 2 OH have been calculated up to the fourth excited torsional state in the vibrational ground state, using an internal axis method (IAM) Hamiltonian. Relative intensities for all possible strong b - and c - type far-infrared (FIR) transitions for K ≤15 in the torsional vibrational ground state have also been reported. Matrix elements for all possible Δ K =±1 transitions have been calculated up to the fourth excited torsional state. The calculations will be useful in the assignments of high resolution far-infrared spectra and optically pumped far-infrared laser lines in this molecular species. The energy levels calculated will provide excellent data base for astrophysical detection in the interstellar space.