Sensitive electric field measurement by fluorescence-dip spectroscopy of Rydberg states of atomic hydrogen

Fluorescence-dip spectroscopy based on an optical double resonance is used to probe the Stark splitting in highly excited Rydberg states of atomic hydrogen. After Doppler-free two-photon excitation to n = 3, fluorescence at Balmer alpha is observed. When the radiation of a second laser is tuned over the resonance between n = 3 and a Rydberg state, the Stark splitting manifests itself as a series of dips in the Balmer-alpha fluorescence intensity. Rydberg states up to n = 55 can be identified. The minimum detectable electric field is 5 V/cm, This is about an order of magnitude more sensitive than other laser-induced fluorescence techniques. [S0031-9007(98)07702-3].