Ab initio potential energy surface and dynamics of He–CO

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Abstract
The potential energy surface for the He–CO van der Waals interaction is calculated by the supermolecular approach using fourth‐order Mo/ller–Plesset perturbation theory (MP4) with a large basis set containing bond functions. The rovibrational energies of He–CO are then calculated by the collocation method. Our ab initio surface has a single near T‐shaped minimum (Rm=3.49 Å, θ=120°, Vm=−20.32 cm−1), in agreement with a recent experimental potential (R=3.394 Å, θ=121.3°, Vm=−22.91 cm−1), determined from high‐resolution spectroscopic measurements, but significantly different from a previously published ab initio surface for this system. The calculated rovibrational energies are in good agreement with experiment. The explicit dependence of the intermolecular potential on the CO bond distance is also studied by MP4 calculations, and the results confirm the experimental observation that the intermolecular coordinates are approximately uncoupled from the CO bond distance.