INFRARED TRANSITION INTENSITIES FOR WATER - A COMPARISON OF AB-INITIOAND FITTED DIPOLE-MOMENT SURFACES

Four surfaces giving the dipole moment for water as a function of inte rnuclear separations are compared. These surfaces are used to predict intensities for transitions involving J = 0 - 1 and Q-branch transitio ns for J = 5 and 10. These intensities are compared with observed tran sition intensities for (H2O)-O-16 from the HITRAN database. For reason s of computational efficiency these calculations were performed with a new discrete variable representation (DVR) transition intensity progr am, DIPOLE3. Our comparisons suggest that the recent ab initio dipole moment surfaces of Gabriel el al. (J. Chem. Phys. 99, 897-900 (1993)) is the most reliable. These surfaces give accurate linestrengths for t ransitions whose intensity vary by nine orders of magnitude and promis e good extrapolation properties. The calculations also point to a numb er of transitions which differ significantly from the values tabulated in HITRAN. (C) 1995 Academic Press, Inc.