Resonant enhancement of dielectronic recombination by a microwave field

We have observed dielectronic recombination of Ba+ and e(-) from a continuum of finite bandwidth in the presence of microwave fields of frequencies 8.08 and 12.05 GHz and amplitudes of up to 2 V/cm. There are sharp resonant enhancements when the microwave frequency matches the Deltan = 1, 2, and 3 resonances of the intermediate autoionizing Rydberg states, and we attribute the enhancements to resonant microwave Stark l mixing. The microwave field provides a simple and powerful way to enhance the recombination rate for incident electrons of a specific energy.