High resolution spectroscopy of Na 5S/sub 1/2/ hyperfine splitting using cold atoms

Summary form only given. A Doppler free measurement of the hyperfine structure splitting (HFS) of 5S/sub 1/2/ level is performed using trapped sodium atoms. We employed two techniques: 1) trap loss enhancement, which consists in the observation of the trapped atom fluorescence when an extra loss channel is created by single photon ionization of the 5S state. This method was not very precise because the lack of absolute reference. 2) Photoionization out of 5S/sub 1/2/ after a two photon excitation from the 3S/sub 1/2/ state.