Isotope effects in ultracold 3D non-adiabatic scattering of Ar–NO

The quantum scattering of Ar and NO in a ²Π electronic state involves two potential energy surfaces (PESs) accessed simultaneously during the collision. This non-adiabatic process is inherently quantum-mechanical and requires a full quantum description that includes the two coupled electronic states. Previously, we developed new three-dimensional potential energy surfaces (A′ and A″) and calculated the bound spectrum of the Ar–NO van der Waals complex. The surfaces were computed using the coupled-cluster CCSD(T) method in the complete basis set limit and were coupled by the spin-orbit interaction. In the present work, we model the “downhill” (exoergic) ²Π_3/2 → ²Π_1/2 inelastic collision of Ar and NO using these two new surfaces. The non-adiabatic process is modeled in the ultracold regime, which is the focus of recent experimental studies. The choice of exoergic pathway and ultracold regime is also computationally favorable. The inelastic cross sections are calculated and analyzed for different values of total angular momentum J and different isotope combinations of N and O.