FREQUENCY RATIO OF AL~(+) AND HG~(+) SINGLE-ION OPTICAL CLOCKS; METROLOGY AT THE 17TH DECIMAL PLACE

摘要

Optical and microwave atomic clock frequency comparisons at NIST over the past several years provide some of the best tests of any present-day, temporal variations of the fundamental constants. Notably, the increasingly precise measurements of the absolute frequency of the Hg~(+) single-ion optical clock and the cesium primary frequency standard NIST-F1, now constrain the fractional variation of the fine structure constant alpha to less than 2(centre dot)10~(-16)yr~(-1). The measurements of the frequency ratio of the Al~(+) and Hg~(+) optical clocks, which now reach a fractional frequency uncertainty of 5.2(centre dot)10~(-17), offer a 10-fold tighter constraint in just one year. The record of such measurements over the last year sensitively tests and restricts any temporal variation of alpha to alpha/alpha velence -1.6 +- 2.3(centre dot)10~(-17)yr~(-1), consistent with zero.