Near-classical noise enhancement of microwave ionization of Rydberg atoms.

The ionization of the highly excited hydrogen atom in a strong external microwave field is a classically chaotic, near-classical quantum system for microwave frequencies somewhat below the initial Kepler electron orbit frequency. The addition of microwave noise is found to reduce the sinewave microwave field needed for ionization, modifying the near-classical fast process responsible for the microwave energy absorption. A classical numerical calculation based upon a many-frequency model of the noise qualitatively reproduces the observed noise enhancement.