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 atmospheric absorption of solar radiation is discussed.

Cis-cis and trans-perp HOONO: Action spectroscopy and isomerization kinetics

“…Kjaergaard et al have observed the same inadequacy of DFT in determination of electrostatic moments in systems with hydrogen bonding in the case of the water dimer. 41 Our ab initio calculations predict that trans-perp HOONO has a larger permanent dipole moment than cis-cis HOONO, and one that points predominantly along the c axis of the molecule. The permanent dipole moment in cis-cis HOONO roughly bisects the a and b axes in the plane of the molecule and points towards the terminal O with a slightly larger component along the b axis than the a axis.…”

OH-Stretch Vibrational Spectroscopy of Hydroxymethyl Hydroperoxide

“…39 More recently, empirically scaled ab initio calculated local-mode parameters combined with ab initio dipole moment function have been successful in predicting OH-stretching spectra of hydrated complexes. 40,41 The advancement in computational methods and hardware now allows high-level ab initio calculations, which can eliminate the need for empirical scaling of the local-mode parameters. For example, the OH-stretching localmode parameters of the different conformers in ethylene glycol were recently calculated with impressive agreement to experiment.…”

The H<sub>2</sub>O-O<sub>2</sub> water vapour complex in the Earth's atmosphere

“…The K p of Vaida and Headrick (2000) shows a peculiar increase, almost linearly proportional to temperature. The K p values of Kjaergaard et al (2002) have a minimum around 225 K and increase at high temperatures, indicating no dissociation of the complex. In both cases the behaviour of K p is not compatible with the estimated structure of the H 2 O-O 2 complex.…”

“…The studies of Vaida and Headrick (2000) and Kjaergaard et al (2002) both used the harmonic oscillator approximation to calculate the partition functions needed to estimate K p . Alternately, Sabu et al (2005) calculated the partition function, and thus K p , using another approach.…”

“…Calculated equilibrium constant K p for H 2 O-O 2 using different methods (after Sabu et al, 2005) . The uppermost line (small square symbols) shows the results of Kjaergaard et al (2002) and the triangle symbols those of Vaida and Headrick (2000). The lines with lozenge and big square symbols are the results of the anharmonic and harmonic calculations of Sabu et al (2005), respectively.…”