Dynamics of Electronically Inelastic and Reactive Collisions of O(¹D) with N₂ Based on Machine-Learned Coupled...

Electronically nonadiabatic transitions can play important roles in the pathways for reactive and energy-transfer processes, especially in high-energy collisions, and their accurate description is essential for many applications, including the simulation of thermal energy content and heat flux in shock-heated air. In the present work, we use extended multistate restricted-active-space second-order perturbation theory (XMS-RASPT2) with automatic learning via compatibilization by deep neural network (CDNN) to obtain the analytic representation of coupled potential energy surfaces (PESs) in the 11-state ¹A″ manifold of N₂O. The compatible potential energy surfaces are analytically tractable, with smooth and continuous behavior and with intersections in regions where the adiabatic curves display discontinuous derivatives and locally avoided crossings. We find that the convenient compatible matrix procedure is successful in globally fitting a dense manifold of states over a wide range of energies. The procedure yields not only a fit to the compatible potential energy matrix (CPEM) and its gradient but also analytic representations of the adiabatic potential energy surfaces and their gradients, including the correct topology of conical intersection seams. By combining the analytic representation of the present global PESs for an 11-state ¹A″ manifold and a slightly modified previously determined representation of a 13-state ¹A' manifold of N₂O, we have enough information to study electronically nonadiabatic and reactive collisions of O(¹D) with $N_2\left(X{}^1{\Sigma }_g^{+}\right)$ by using the semiclassical asymptotically extended curvature-driven coherent switching with decay of mixing (AE-κCSDM) method, and we used this method to calculate cross sections for these collisions as functions of relative translational energy and initial vibrational and rotational energy. This reveals that reactive collisions dominate over electronically inelastic nonreactive collisions, with the most competitive electronically inelastic nonreactive channel leading to $N_2\left(X\right)+O\left({}^{1}S\right)$ formation. The calculated cross sections of high-energy collisions of N₂ with O(¹D) can be used for simulating thermal energy content and heat flux in shock-heated air.