Time-gated photoionization spectroscopy demonstrated for cesium Rydberg wave packets in an electric field

We introduce a new spectroscopic technique in which electron emission after optical excitation is measured with picosecond time resolution using a streak camera. By scanning the frequency of the exciting laser and measuring the electron flux in certain time gates, time-gated photoionization spectra are obtained. The technique is demonstrated for cesium Rydberg wave packets in an electric field of 1.0 kV/cm. The electron ejection probability is enhanced when the radial and angular oscillation periods of the excited wave packet are commensurable.