Abstract
Light shifts of the ground state HFS transition in a 133Cs vapour, produced by a CW narrow-band tunable GaAs laser matched to the D2 resonance line have been investigated. The 0-0 transition microwave frequency was accurately measured as a function of the laser frequency. For usual optical-pumping light intensities, excellent agreement is found with theory. At higher intensities, distortions appeared in the resonance curves. A new frequency-stabilization method of lasers is suggested.