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

We have calculated the fundamental and overtone OH-stretching vibrational band intensities of the water−nitrogen (H 2 O·N 2 ) and water−oxygen (H 2 O·O 2 ) 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 H 2 O·N 2 and H 2 O·O 2 complexes are weakly bound and the individual molecular units are only slightly perturbed by complexation, unlike what is found for the water dimer (H 2 O·H 2 O) and the water−nitric acid complex (H 2 O·HNO 3 ). The fundamental OH-stretching intensity in H 2 O·N 2 is enhanced and the first overtone intensity weakened compared to H 2 O as an effect of the hydrogen bonding. In H 2 O·O 2 the OH-stretching intensities are comparable to those of H 2 O. On a per water unit basis, the calculated OH-stretching intensities of the higher overtones of H 2 O·N 2 and H 2 O·O 2 are similar to those of H 2 O·H 2 O. The possible effect of H 2 O·N 2 and H 2 O·O 2 on the atmospheric absorption of solar radiation is discussed.