J. Jortner et M. Bixon, INTRAMOLECULAR DYNAMICS AND CHARGE SEPARATION IN LARGE SYSTEMS, Berichte der Bunsengesellschaft fur Physikalische Chemie, 99(3), 1995, pp. 296-309
Citations number
83
Categorie Soggetti
Chemistry Physical
Journal title
Berichte der Bunsengesellschaft fur Physikalische Chemie
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.