DYNAMICS OF SEQUENTIAL QUANTUM TUNNELING

We calculate numerically the time evolution of a quantum wave packet c onfined to a potential well bound by a finite barrier on one side. Bec ause of the period oscillations in the well, the wave packet ejects se quentially tunneled components into the free space. We choose two mode ls: one representing adiabatic molecular energy levels and the other o ne representing a semiconductor heterostructure. After scaling, the tw o problems are found to cover the same variable ranges for physically relevant parameters. We also use two numerical methods: one based on d irect integration of Schrodinger's equation, the split-operator method , the other one utilizing a semiclassical path summation approach. In all cases we find the motion of the trapped wave packet cooled because of the filtering effect provided by the preferred tunneling of high e nergy components at consequtive tunneling events. This interpretation is confirmed by a comparison with an approximate analytic evaluation o f the sequential tunneling probabilities.