Quantum and statistical state-to-state studies of cold Ar + H 2 + collisions.

In this work we present new state-to-state integral scattering cross sections and initial-state selected rate coefficients for the 36 Ar ( 1 S) + H 2 + (X 2 Σ g + , v = 0, j ) reactive system for collision energies up to 0.1 eV (with respect to the 36 Ar ( 1 S) + H 2 + (X 2 Σ g + , v = 0, j = 0) channel). To the best of our knowledge, these cross sections are the first fully state resolved ones that were obtained by performing time-independent quantum mechanical and quantum statistical calculations. For this purpose a new full-dimensional ground state 2 A' adiabatic electronic potential energy surface was calculated at the MRCI+Q/aug-cc-pVQZ level of theory, which was fitted by means of machine learning methods. We find that a statistical quantum method and a statistical adiabatic channel model reproduce quantum mechanical initial-state selected cross sections fairly well, thus suggesting that complex-forming mechanisms seem to be playing an important role in the reaction dynamics of the reaction that was studied.