High-resolution synchronized-quantum-beat spectroscopy using modulation sidebands: measurement of pressure shifts of the hyperfine splitting in sodium 3^2S_1/2

Abstract

Pressure shifts of the hyperfine splitting in Na 3²S_1/2 that are due to buffer gases have been measured for the first time to our knowledge by all-optical means using the method of synchronized-quantum-beat spectroscopy reported previously [Y. Fukuda et al., Opt. Commun. 38, 357 (1981)]. The substate coherence is excited and detected with amplitude-modulated mode-locked laser pulses tuned to the D₁ line (pulse-repetition frequency, f_p; modulation frequency, f_m), and the resonances observed at f₀ = nf_p + n′f_m (n and n′ are integers) are used for the measurement. The pressure-shift coefficients obtained at 210°C are 82, 61, −1, and −47 Hz/Torr for He, N₂, Ar, and Kr, respectively, within an accuracy of ±3 Hz/Torr.