Dynamics of very high molecular Rydberg states: The intramolecular processes

Classical trajectory computations are used to document and examine the purely intramolecular decay dynamics of very high Rydberg states of an isolated cold molecule. The Hamiltonian is that of an anisotropic ionic core about which the Rydberg electron revolves. The equations of motion are integrated using action angle variables in order to ensure numerical stability for many orbits of the electron. Examination of individual trajectories verifies that both "up" and "down" intramolecular processes are possible. In these, the electron escapes from the detection window by a gain or loss of enough energy. Either process occurs in a diffusive like fashion of many smaller steps, except for a very small fraction of prompt processes. The results for ensembles of trajectories are examined in terms of power spectra of the different modes of motion and in terms of the decay kinetics. More than one time scale can be discerned in the intramolecular decay kinetics and the faster decay occurs on a nanosecond time scale. The fraction of faster decaying trajectories which exit by an up or a down process does vary with the initial energy.