Phase-Dependent Electron-Ion Recombination in a Microwave Field

Using picosecond laser photoionization of Li in a microwave field we have observed phase-dependent recombination of the photoelectrons with their parent Li+ ions. Recombination occurs at phases of the microwave field such that energy is removed from the photoelectron in the first microwave cycle after excitation, and there are two maxima in the recombination in each microwave cycle. These observations are consistent with observations made using an attosecond pulse train phase locked to an infrared pulse and with the ''simpleman's'' model, modified to account for the fact that the photoelectrons are produced in a Coulomb potential.