@article{a2299ee00c5e11df825d000ea68e967b,
title = "The absolute frequency of the 87Sr optical clock transition",
abstract = "The absolute frequency of the 1S0{\textendash}3P0 clock transition of 87Sr has been measured to be 429 228 004 229 873.65 (37) Hz using lattice-confined atoms, where the fractional uncertainty of 8.6 {\texttimes} 10-16 represents one of the most accurate measurements of an atomic transition frequency to date. After a detailed study of systematic effects, which reduced the total systematic uncertainty of the Sr lattice clock to 1.5 {\texttimes} 10-16, the clock frequency is measured against a hydrogen maser which is simultaneously calibrated to the US primary frequency standard, the NIST Cs fountain clock, NIST-F1. The comparison is made possible using a femtosecond laser based optical frequency comb to phase coherently connect the optical and microwave spectral regions and by a 3.5 km fibre transfer scheme to compare the remotely located clock signals.",
author = "Campbell, \{Gretchen K.\} and Ludlow, \{Andrew D.\} and Sebastian Blatt and Thomsen, \{Jan W.\} and Martin, \{Michael J.\} and \{de Miranda\}, \{Marcio H. G.\} and Tanya Zelevinsky and Boyd, \{Martin M.\} and Jun Ye and Diddams, \{Scott A.\} and Heavner, \{Thomas P.\} and Parker, \{Thomas E.\} and Jefferts, \{Steven R.\}",
year = "2008",
doi = "10.1088/0026-1394/45/5/008",
language = "English",
volume = "45",
pages = "539--548",
journal = "Metrologia",
issn = "0026-1394",
publisher = "IOP Publishing",
number = "5",
}