Accurate ab initio near-equilibrium potential energy and dipole moment functions of HOCl and HOBr

Abstract

Accurate three-dimensional, near-equilibrium potential energy and electric dipole moment surfaces have been computed for HOCl and HOBr using the CCSD(T) method with large correlation consistent basis sets. The analytical potential energy and dipole moment functions have been used in perturbational and variational calculations of the anharmonic spectroscopic constants and vibrational spectra of HOCl/DOCl and HOBr/DOBr. Excellent agreement with experiment is observed for the fundamentals and low-lying overtones and combination bands. The calculated IR spectra and intensities of HOBr are calculated to be very similar to those of HOCl. In general, the calculated intensities of the deuterated species are weaker by about a factor of two, but have the same general features. An exception is the ν 2 + 3ν 3 combination band of DOBr, which is predicted to borrow intensity from the strong ν 1 band, resulting in a significant calculated band intensity of the same magnitude as the ν 3 fundamental.