Model calculations of the UV charge transfer (CT) absorption spectrum of a water-oxygen collision pair are reported. The motivation is an assessment of this process as the initial stage of a new nucleation mechanism for atmospheric water vapor. Ab initio MP2(full)/6-311++G(2d,p) geometries of ground state van der Waals dimers and (complete active space self-consistent field) CAS-SCF(10,7)/6-311++G(2d,p) geometries of the CT state are detailed. MR-ACPF/6-311++G(2d,p) potential surfaces have been calculated along the intermolecular coordinate. The bound and continuum nuclear wave functions have been calculated numerically on these potential curves and, with the MR-CISD/6-311++G(2d,p) electronic transition dipole moment integral, used to calculate the unary and binary absorption coefficients. The implications of the results for explaining water photonucleation in the presence of oxygen are discussed.