V. Kondratovich et al., Classically forbidden recurrences in the photoabsorption spectrum of lithium - art. no. 043409, PHYS REV A, 6204(4), 2000, pp. 3409
We present data on the photoabsorption spectrum of lithium atoms in an elec
tric field at energies between the saddle point of the Stark potential and
below the field-free ionization threshold. The spectrum displays a sequence
of sharp resonances and a sequence of broad ones. We find that the broad r
esonances arise from the classically forbidden reflection of waves above a
dynamical potential barrier. The recurrence spectrum is also observed and i
t is dramatically affected by above-barrier reflections. We have developed
a semiclassical theory that interprets the spectra using quasiclassical tra
jectories that undergo above-barrier reflection.