Classical models for electronic degrees of freedom: Derivation via spin analogy and application to F*+H2→F+H2

By invoking the formal equivalence of a finite level quantum mechanical system to a quantum spin in an external field, this paper shows how a classical model can be constructed for an arbitrary finite level quantum system. For two‐state and three‐state cases this leads to the same classical Hamiltonian that was obtained earlier by other more heuristic methods, but it shows how to treat the general F‐state case. The purpose of this overall approach is to be able to represent the electronic states in electronically nonadiabatic collision processes by a classical degree of freedom so that all degrees of freedom, electronic and heavy particle (i.e., translation, rotation, and vibration) can be treated on a consistent dynamical footing. Application of this model to the quenching of F* (2P1/2) by collisions with H2 is described, and this completely classical approach is seen to give excellent agreement with the quantum mechanical coupled channel calculations of Rebentrost and Lester.