Potential energy surface and intermolecular vibrations of O2–H2O

The potential energy surface (PES) of O2–H2O was studied by second-order Møller–Plesset perturbation and multi-reference single- and double-excitation configuration interaction (MRSDCI) methods with aug-cc-pVTZ basis sets. The in-plane mutual rotations of the monomers and the intermolecular stretching were also investigated by numerically solving the Schrödinger equation for nuclear motions with the three-dimensional finite element method. The lowest states for the conrotatory motion are actually degenerate, while those for the disrotatory one are split by 6.9 cm−1, which is consistent with the recent result of Fourier-transform microwave spectroscopy, where the C2v structure was obtained.