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

For the interaction of OH(X(2)Π) 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).