Journal of Physical Chemistry A, Vol.119, No.20, 4763-4779, 2015
First Predictions of Rotationally Resolved Infrared Spectra of Dideuteromethane ((CH2D2)-C-12) From Potential Energy and Dipole Moment Surfaces
We report the variationally computed infrared spectrum of (CH2D2)-C-12 using our recent potential energy and dipole moment methane surfaces, which have been initially derived in the irreducible tensor representation adapted to the tetrahedral symmetry of the major isotopologue (CH4)-C-12. The nuclear motion calculations are accomplished by combining the normal-mode Eckart-Watson Hamiltonian with isotopic and symmetry transformations. Our direct vibrational calculations are compared to the 93 observed band centers up to 6300 cm(-1). Except for two outliers the root-mean-square deviation is 0.22 cm(-1) and the maximum error is 0.7 cm(-1) without empirical adjustment of parameters. The work aims at filling the gap concerning missing line strength information for this molecule. Theoretical spectra predictions are given up to J = 25 and, for the very first time, ab initio intensity predictions for rovibrational line transitions are in good qualitative agreement with available experimental spectra.