Abstract

Intense and narrow resonances in pumpprobe geometry have been recently observed in laser cooled atomic vapors.^[1,2] These resonances were attributed to Raman processes between light-shifted ground state Zeeman sublevels which are differentially populated by the cooling lasers.^[1] We show here that Raman spectroscopy is also a powerful tool to probe the atom external degrees of freedom. We have observed ultranarrow resonances in a ID Cesium optical molasse which are due to the oscillation of atoms in the periodic potential wells associated with the light-shifts. Raman spectroscopy gives direct access to the oscillation frequency (position of the resonances) as well as damping time of the oscillation (width of the resonances.). Furthermore, this experiment provides a serious support for the theory of atomic band structures in optical molasses.^[3] This experiment is to be related to the experiment of Westbrook et al.^[4] which proved the atom localisation by observing Dicke narrowing in the fluorescence spectrum.

© 1992 IQEC