Abstract

We report here on the observation of extra sub-Doppler resonances in the vicinity of the third resonance line of Cs (6S→8P) at 388 nm (6S_1/2-8P_3/2) and 389 nm (6S_1/2-8P₁₂), when saturated absorption spectroscopy is usually expected to provide a frequency reference in the analysis of other physical processes [1]. Our experiments show that when the pump and probe are relatively intense (typically ≥ 10 mW/mm, ²), there are some additional narrow lines inside the Doppler width (see fig. 1), aside from the narrow expected saturated absorption components that allow to resolve the structure of the hyperfine manifolds of Cs (8P). Because of the weak (~10^-3) oscillator strength of these transitions, heating up of the Cs vapour -to enhance Cs atomic density-, and focusing of the beams -in order to saturate-, are required to record a saturated absorption spectrum. However, for the various cells that we have used (length : 1-5 cm), a typical temperature of 70-100 °C was sufficient, and we could even record signals at T ~ 45°C, corresponding to a Cs atomic density as low as 5.10¹¹at/cm³.

© 2009 IEEE