High-order impulse approximation for calculating pulsed-field recombination

In a recent paper, Bensky et al. [Phys. Rev. Lett. 81, 3112 (1998)] experimentally reattached an outgoing continuum electron to an ion using a pulsed electric field. Quantum and classical calculations are presented that illustrate the importance of various mechanisms for this reattachment process. The quantum calculations are based on a high-order impulse approximation. Both calculations support the idea that after an initial rapid dispersal, the bound part of the wave packet reforms after one Rydberg period; it continues to reform out to long times. A quantum calculation of the electron flux ejected from Ca Rydberg states in a static electric field suggests that classical calculations should not accurately describe pulsed-field recombination in the presence of a static field unless the atom is H or the fields are very weak; this observation agrees with experiment.