Sensitive Electric Field Measurement by Fluorescence-Dip Spectroscopy of Rydberg States of Atomic Hydrogen

Abstract

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 $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3$, fluorescence at Balmer $\ensuremath{\alpha}$ is observed. When the radiation of a second laser is tuned over the resonance between $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3$ and a Rydberg state, the Stark splitting manifests itself as a series of dips in the Balmer- $\ensuremath{\alpha}$ fluorescence intensity. Rydberg states up to $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}55$ can be identified. The minimum detectable electric field is $5\mathrm{V}/\mathrm{cm}$. This is about an order of magnitude more sensitive than other laser-induced fluorescence techniques.