The interaction of OH(X²Π) with H2: Ab initio potential energy surfaces and bound states.

For the interaction of OH(X²Π) with H₂, under the assumption of fixed OH and H₂ bond distances, we have determined two new sets of four-dimensional ab initio potential energy surfaces (PES's). The first set of PES's was computed with the multi-reference configuration interaction method [MRCISD+Q(Davidson)], and the second set with an explicitly correlated coupled cluster method [RCCSD(T)-F12a] sampling the subset of geometries possessing a plane of symmetry. Both sets of PES's are fit to an analytical form suitable for bound state and scattering calculations. The CCSD(T) dissociation energies (D₀) of the OH-para-H₂ and the OH-ortho-H₂ complexes are computed to be 36.1 and 53.7 cm^-1. The latter value is in excellent agreement with the experimental value of 54 cm^-1. [ABSTRACT FROM AUTHOR]