Knowledge Bank

A microscopic dynamical treatment of chemical systems comprising both light particles that require a quantal description and heavy ones that may be described adequately by classical mechanics is briefly reviwed. A (partial) classical limit of Heisenbergs equations yields a self -consitent set of “hemiquantal’s” equations (HQE) of motion. The adibatic limit of the HQE,in which energy is not shared between high frequency modes of the classical subsystems, is applied to a one -dimensional model for infrared absorption by matrix -isolated impurities .The predictions of the model are consistent with recent experimental measurement on the ”Q” feature of $HC\ell$ isolated in Ar.