Calculated OH-Stretching Vibrational Transitions in the Water−Nitrogen and Water−Oxygen Complexes

Abstract

We have calculated the fundamental and overtone OH-stretching vibrational band intensities of the water−nitrogen (H2O·N2) and water−oxygen (H2O·O2) complexes. The calculations use the harmonically coupled anharmonic oscillator local mode model with local mode parameters obtained from scaled ab initio calculations and ab initio calculated dipole moment functions. The H2O·N2 and H2O·O2 complexes are weakly bound and the individual molecular units are only slightly perturbed by complexation, unlike what is found for the water dimer (H2O·H2O) and the water−nitric acid complex (H2O·HNO3). The fundamental OH-stretching intensity in H2O·N2 is enhanced and the first overtone intensity weakened compared to H2O as an effect of the hydrogen bonding. In H2O·O2 the OH-stretching intensities are comparable to those of H2O. On a per water unit basis, the calculated OH-stretching intensities of the higher overtones of H2O·N2 and H2O·O2 are similar to those of H2O·H2O. The possible effect of H2O·N2 and H2O·O2 on the atmos...