Determination of the Rydberg constant by direct frequency measuremen

We have built a frequency chain to connect the frequencies of the 2S-8S/D two-photon transitions in hydrogen to two optical standards, the methane-stabilized He-Ne laser and the iodine-stabilized He-Ne laser. In this way, an optical frequency of atomic hydrogen is directly linked for the first time to the cesium clock without any interferometry. We deduce a new value for the Rydberg constant with an uncertainty of 2.2 parts in 10(11). This value is in very good agreement with published values. The same frequency scheme has been used to measure the frequencies of the 5S-5D two-photon transition in rubidium and 2(3)S(1-)3(3)P(o) in helium.