DYNAMICS OF ULTRAHIGH MOLECULAR RYDBERGS IN WEAK ELECTRIC-FIELDS

In this paper we explore the dynamics of the mixed Stark manifold of u ltrahigh Rydberg states (principal quantum number n = 50-250) of the l arge molecules interrogated by time-resolved ZEKE (zero-electron kinet ic energy) spectroscopy. We pursue the formal analogy between the coup ling, accessibility, and decay of ultrahigh Rydbergs in an external we ak (F = 0.01-1.0 V/cm) electric field and intramolecular (interstate a nd intrastate) relaxation in a bound level structure. The effective Ha miltonian formalism with several doorway and escape states was advance d to treat the dynamics. The theory accounts for thr dilution effect, i.e., the dramatic lengthening of the lifetimes of ultrahigh Rydbergs, relative to that expected on the basis of the n(-3) scaling law for t he decay widths. Model calculations for the field-induced (I) mixing r eveal that die Rydberg time-resolved population probability is charact erized by two distinct (similar to ns and similar to mu s) time scales . To date, long time-resolved (10 mu s-100 ns time scales) nonexponent ial decay of ZEKE Rydbergs was experimentally documented, in accord wi th our analysis. The predicted existence of the short decay times (1-1 0 ns) was not yet subjected to an experimental test. Next, we extend t he model calculations to treat the mixing of several n manifolds, demo nstrating that in the strong mixing limit the overall features of the temporal decay are similar to that of a single n manifold.