Dissipative tunneling, breathers and anomalous decay in doped alkali halides

In studying the decay kinetics of the excited states in alkali halides doped with heavy impurities, anomalous behaviour in the slow emission, consisting of several decay components, was found. New efforts were made to interpret this behaviour by invoking delicate and sophisticated mechanisms which transcend the systems considered. The evolution of the lattice reaction time is fundamental to this purpose, and requires Jahn-Teller models able to interpret the slow complex decay of the emission in the A-band. One model is based on the formation and confinement of discrete breathers, as a result of the Jahn-Teller cluster distortion, whose temporal stability is of the same order as the luminescence decay time (ms). Another model is based on a dissipative tunneling process, the duration of which strongly depends on the consistency of the barrier and presents a very large variation of the decay time (from ns to ms). An attempt is here made for a unification of the two mechanisms.