Doppler-free Selective Reflection spectroscopy of the 6s ² S 1/2 → 7p ² P 3/2 transition of Caesium using an optical nanocell

Selective Reflection (SR) spectroscopy of the 6 s 2 S 1/2 → 7 p 2 P 3/2 electric dipole transition of Caesium (λ = 456 nm) is performed for the first time using a nanometric thin cell ( L = 50 - 1500 nm, T = 200 °C). We successfully form narrow resonances corresponding to the F g = 3, 4 → F e = 2, 3, 4, 5 hyperfine transitions. All transitions are well spectrally resolved and the geometry of the cell allows us to obtain a strong 30 times narrowing of the Doppler width with a single beam pass. For lower thicknesses ( L < 400 nm), we observe a red shift of the SR lines which we attribute to atom-surface interactions, and provide estimates of the C 3 interaction coefficient. The oscillator strengths of the 6 s 2 S 1/2 → 7 p 2 P 3/2 hyperfine transitions are about two orders of magnitude than that of Cs D 2 line. Experimental measurements are in good agreement with theoretical calculations. We emphasize the advantage of nanocell spectroscopy compared to the well known Saturated Absorption method, and present possible applications.