Frequency measurement of the 2S-12D transitions in hydrogen and deuterium. New determination of the Rydberg constant

We have performed the first pure frequency measurement of the 2S-12D two-photon transitions in atomic hydrogen and deuterium. These frequencies are compared to two optical standards, the CO/sub 2/ laser stabilized on the OsO/sub 4/ molecule and the optical rubidium laser standard (LD/Rb) (namely a laser diode at 778 nm stabilized on the 5S/sub 1/2/-5D/sub 5/2/ two-photon transition of rubidium). We have built a frequency chain to connect the hydrogen lines to the frequency standards. The main part of the experiment is located in the LKB laboratory, one part of the frequency chain is in the LPTF laboratory, two optical fibers linked the two parts of this experiment.