  We report on the measurement of electron emission after the interaction of
strong laser pulses with atoms and molecules. These electrons originate from
high-lying Rydberg states with quantum numbers up to $n \lesssim 120$ formed by
frustrated field ionization. Simulations show that both tunneling ionization by
a weak dc field and photoionization by the black-body radiation contribute to
delayed electron emission on the nano- to microsecond scale. We measured
ionization rates from these Rydberg states by coincidence spectroscopy.
Further, the dependence of the Rydberg-state production on the ellipticity of
the driving laser field proves that such high-lying Rydberg states are
populated through electron recapture. The present experiment provides detailed
quantitative information on Rydberg production by frustrated field ionization.
