Three-dimensional potential energy surfaces of ArNO (X̃ ²Π)

Until now, the potential energy surfaces (PESs) of the ArNO complex found in the literature were two-dimensional, with the NO interatomic distance being fixed. In this work, we present the first accurate three-dimensional ground state X̃ ²Π PESs (both A' and A″) of ArNO computed at the CCSD(T)/CBS level of theory. The equilibrium geometries and the well depths (D_e) are compared to several other electronic structure methods. We found that using the multireference method, MRCI-F12 makes the surfaces much shallower (by 25%) and the depth of the surfaces does not agree with experimental data. The explicitly correlated coupled-cluster method underestimates the well depth as well. Analytic representations for both A' and A″ surfaces were fit to 4380 ab initio points to within 2.71 cm^-1. A three-dimensional Numerov propagator method in Delves coordinates is used to compute the bound state spectrum up to J_tot = 6.5. The recommended dissociation energies are D₀ = 97.2 cm^-1 for the adiabatic ground state and D_e = 133.7 (128.1) cm^-1 for A' (A″).