title: Measurement of the hydrogen 1S- 2S transition frequency by phase coherent comparison with a microwave cesium fountain clock
abstract: We report on an absolute frequency measurement of the hydrogen 1S-2S two-photon transition in a cold atomic beam with an accuracy of 1.8 parts in 10(14). Our experimental result of 2 466 061 413 187 103(46) Hz has been obtained by phase coherent comparison of the hydrogen transition frequency with an atomic cesium fountain clock. Both frequencies are linked with a comb of laser frequencies emitted by a mode locked laser.
authors.affiliation: Max-Planck-Institut fur Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany.
authors.initials: M
authors.lastname: Niering
authors.initials: R
authors.lastname: Holzwarth
authors.initials: J
authors.lastname: Reichert
authors.initials: P
authors.lastname: Pokasov
authors.initials: T
authors.lastname: Udem
authors.initials: M
authors.lastname: Weitz
authors.initials: TW
authors.lastname: Hansch
authors.initials: P
authors.lastname: Lemonde
authors.initials: G
authors.lastname: Santarelli
authors.initials: M
authors.lastname: Abgrall
authors.initials: P
authors.lastname: Laurent
authors.initials: C
authors.lastname: Salomon
authors.initials: A
authors.lastname: Clairon