Selective excitation of Rydberg levels in atomic hydrogen by three photon absorption

A tunable UV laser with 400 kW peak power is utilized to achieve selective excitation of Rydberg levels in atomic hydrogen by three photon transitions from the ground state. Focused UV power densities on the order of 109 W/cm2 are shown to be sufficient to produce easily detectable excitations of states with principle quantum number n as high as 35. Significant level shifts due to the AC Stark effect are observed. © 1979.