INTRAMOLECULAR DYNAMICS AND CHARGE SEPARATION IN LARGE SYSTEMS

We adopt the theory of intramolecular dynamics to explore charge separ ation and recombination in two classes of 'isolated' solvent-free mole cular systems: (A) Supermolecules containing bridged electron donor an d electron acceptor, where electron transfer occurs on a spatial scale of similar to 10 Angstrom. (B) Ultrahigh molecular Rydberg excitation s with a principle quantum number n similar or equal to 50-300 and spa tial dimensions of similar to 10(4) Angstrom, where relaxation process es, e.g., electron-core recombination via internal conversion or predi ssociation, and charge separation by autoionization, are manifested. T he molecular limit for photoinduced long-range ET in isolated supermol ecules [class (A)] is treated on the basis of the statistical limit fo r interstate radiationless transitions, which involve either a direct or a mode-selective mediated coupling. The level structure, optical ex citation modes and dynamics of high molecular Rydbergs [class (B)] int errogated by time-resolved ZEKE (zero-electron kinetic energy) spectro scopy, are treated by the effective Hamiltonian formalism. We pursue t he formal analogy between the coupling, accessibility and decay of ult rahigh Rydbergs in an external weak (F = 0.01-1.0 V/cm) electric field and intramolecular (interstate and intrastate) relaxation in a bound level structure. Model calculations for the field-induced (l) mixing r eveal that the Rydberg dynamics is characterized by two distinct (simi lar to ns and similar to mu s) time scales. Up to date, long time-reso lved (10 mu s-100 ns time scales) nonexponential decay of ZEKE Rydberg s was experimentally documented, in accord with our analysis. The pred icted existence of the short decay times (1-10 ns) was not yet subject ed to an experimental test.