Effects of monomer flexibility on spectra of N2–HF

The interaction energies of N2–HF were computed ab initio on a five-dimensional grid, including the dependence on the H–F separation. The coupled-cluster method with up to noniterative triple excitations was employed and the interaction energies were extrapolated to the complete basis set limit. These energies were then averaged over the vibrational wave functions of HF corresponding to the ground and the third excited states and two four-dimensional potential energy surfaces were fitted to these values. Rovibrational calculations performed using these surfaces gave dissociation energies, fundamental frequencies, rotational constants, and distortion constants in excellent agreement with experimental values.