title: Two-dimensional H2O-Cl2 and H2O-Br2 potential surfaces: an ab initio study of ground and valence excited electronic states.
abstract: All electron ab initio calculations for the interaction of H2O with Cl2 and Br2 are reported for the ground state and the lowest triplet and singlet Pi excited states as a function of both the X-X and O-X bond lengths (X = Cl or Br). For the ground state and lowest triplet state, the calculations are performed with the coupled cluster singles, doubles, and perturbative triple excitation level of correlation using an augmented triple-zeta basis set. For the 1Pi state the multireference average quadratic coupled cluster technique was employed. For several points on the potential, the calculations were repeated with the augmented quadruple-zeta basis set. The ground-state well depths were found to be 917 and 1,183 cm-1 for Cl2 and Br2, respectively, with the triple-zeta basis set, and they increased to 982 and 1,273 cm-1 for the quadruple-zeta basis set. At the geometry of the ground-state minimum, the lowest energy state corresponding to the unperturbed 1Pi states of the halogens increases in energy by 637 and 733 cm-1, respectively, relative to the ground-state dissociation limit of the H2O-X2 complex. Adding the attractive ground-state interaction energy to that of the repulsive excited state predicts a blue-shift, relative to that of the free halogen molecules, of approximately 1,600 cm-1 for H2O-Cl2 and approximately 2,000 cm-1 for H2O-Br2. These vertical blue-shifts for the dimers are greater than the shift of the band maximum upon solvation of either halogen in liquid water.
authors: Centro de Investigaciones Químicas, UAEM, Cuernavaca, Mor. 62210, México. ramon@buzon.uaem.mx
authors: Ramón
authors: R
authors: Hernandez-Lamoneda
authors: Victor Hugo Uc
authors: VH
authors: Rosas
authors: Margarita I Bernal
authors: MI
authors: Uruchurtu
authors: Nadine
authors: N
authors: Halberstadt
authors: Kenneth C
authors: KC
authors: Janda