Ab initio calculations of anharmonic vibrational transition intensities of trans-2,3-dideuteriooxirane

The quartic force field and the cubic dipole moment surface are calculated for trans-2,3- dideuteriooxirane at the self-consistent field and the second order Möller–Plesset levels of theory using a triple zeta plus two polarization functions basis set. Contact transformation theory is used to determine the corresponding anharmonic vibrtional frequencies and intensities. Inclusion of anharmonicity improves agreement of the calculated frequencies and intensities with their experimental counterparts. The anharmonic corrections are much more sensitive to correlation effects for intensities than for frequencies.