title: Absolute frequency measurement of the 40Ca+ 4s(2)S_(1/2)-3d(2)D_(5/2) clock transition.
abstract: We report on the first absolute transition frequency measurement at the 10;{-15} level with a single, laser-cooled 40Ca+ ion in a linear Paul trap. For this measurement, a frequency comb is referenced to the transportable Cs atomic fountain clock of LNE-SYRTE and is used to measure the 40Ca+ 4s ;{2}S_{1/2}-3d ;{2}D_{5/2} electric-quadrupole transition frequency. After the correction of systematic shifts, the clock transition frequency nu_{Ca;{+}}=411 042 129 776 393.2(1.0) Hz is obtained, which corresponds to a fractional uncertainty within a factor of 3 of the Cs standard. In addition, we determine the Landé g factor of the 3d;{2}D_{5/2} level to be g_{5/2}=1.200 334 0(3).
authors.affiliation: Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors.forename: M
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authors.lastname: Chwalla
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authors.initials: J
authors.lastname: Benhelm
authors.forename: K
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authors.lastname: Kim
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authors.lastname: Kirchmair
authors.forename: T
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authors.lastname: Monz
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authors.initials: M
authors.lastname: Riebe
authors.forename: P
authors.initials: P
authors.lastname: Schindler
authors.forename: A S
authors.initials: AS
authors.lastname: Villar
authors.forename: W
authors.initials: W
authors.lastname: Hänsel
authors.forename: C F
authors.initials: CF
authors.lastname: Roos
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authors.lastname: Blatt
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authors.lastname: Abgrall
authors.forename: G
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authors.lastname: Santarelli
authors.forename: G D
authors.initials: GD
authors.lastname: Rovera
authors.forename: Ph
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authors.lastname: Laurent