Improved Measurement of the Hydrogen $1S--2S$ Transition Frequency

Christian G. Parthey, Arthur Matveev, Janis Alnis, Birgitta Bernhardt, Axel Beyer, Ronald Holzwarth, Aliaksei Maistrou, Randolf Pohl, Katharina Predehl, Thomas Udem, Tobias Wilken, Nikolai Kolachevsky, Michel Abgrall, Daniele Rovera, Christophe Salomon, Philippe Laurent, Theodor W. Hänsch

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We have measured the 1S–2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f1S–2S=2 466 061 413 187 035 (10)   Hz for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The improvement to a fractional frequency uncertainty of 4.2×10−15 arises mainly from an improved stability of the spectroscopy laser, and a better determination of the main systematic uncertainties, namely, the second order Doppler and ac and dc Stark shifts. The probe laser frequency was phase coherently linked to the mobile cesium fountain clock FOM via a frequency comb.
Original languageEnglish
Pages (from-to)203001
Number of pages5
JournalPhysical Review Letters
Publication statusPublished - 1 Nov 2011
Externally publishedYes

Fields of Expertise

  • Advanced Materials Science

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