Excited states of OH-(H₂O)n clusters for n = 1-4: an ab initio study.

Equation of motion coupled cluster calculations were performed on various structures of OH in clusters with one, two, three, and four water molecules to determine the energies of valence and charge transfer states. Motivation for these calculations is to understand the absorption spectrum of OH in water. Previous calculations on these species have confirmed that the longer wavelength transition observed is due to the A((2)∑) ← X((2)∏) valence transition, while the shorter wavelength transition is due to a charge-transfer from H2O to OH.

Atmospheric significance of water clusters and ozone-water complexes.

Ozone-water complexes O3···(H2O)n (n = 1-4) have been theoretically investigated using QCISD and CCSD(T) methods along with the 6-311G(2df,2p), 6-311+G(2df,2p), aug-cc-pVDZ, aug-cc-pVTZ, and aug-cc-pVQZ basis sets and extrapolation to CBS limit. For comparison, water clusters (H2O)n (n = 1-4) have also been studied at the same level of theory. The ozone-water complexes are held together by a combination of weak specific hydrogen-bonding and van der Waals interactions.