Towards an absolute measurement of the 1S3S line in atomic hydrogen

For very high-precision spectroscopy such as the two photon 1S–nS transitions in hydrogen, the ability to measure precisely the absolute frequency of the excitation laser is required together with the best possible signal-to-noise ratio for the fluorescence signal. In the context of our experiment on the 1S–3S transition, we present the specificities of our optical frequency comb apparatus, as well as a new detection scheme that makes use of the spatial information provided by a CCD camera detector.PACS No.: 39.30.+w