Velocity-selective spectroscopy measurements of Rydberg fine structure states in a hot vapor cell.

A velocity-selective spectroscopy technique for studying the spectra of Rydberg gases is presented. This method provides high-resolution spectrum measurements. We present experimental results for a ladder system 6S1/2 → 6P3/2 →nS(D) electromagnetically-induced transparency involving highly-excited Rydberg states. Based on a radio-frequency modulation technique, we measure the hyperfine structure splitting of intermediate states and the fine structure splitting of Rydberg states in a room temperature 133Cs vapor cell. The experimental data and theoretical predictions show excellent agreement. [ABSTRACT FROM AUTHOR]