Title

Recent atomic clock comparisons at NIST

Abstract

The record of atomic clock frequency comparisons at NIST over the past half-decade provides one of the tightest constraints of any present-day temporal variations of the fundamental constants. Notably, the 6-year record of increasingly precise measurements of the absolute frequency of the Hg+ single-ion optical clock (using the cesium primary frequency standard NIST-F1) constrains the temporal variation of the fine structure constant α to less than 2 · 10−6yr−1 and offers a Local Position Invariance test in the framework of General Relativity. The most recent measurement of the frequency ratio of the Al+ and Hg+ optical clocks is reported with a fractional frequency uncertainty of ±5.2 · 10−17. The record of such measurements over the last year sensitively tests for a temporal variation of α and constrains α˙/α=(−1.6±2.3) . 10−17yr−1, consistent with zero.

Publisher

Springer Berlin

Publication Date

10-1-2008

Publication Title

The European Physical Journal Special Topics

Department

Physics and Astronomy

Document Type

Article

DOI

10.1140/epjst/e2008-00807-7

Language

English

Format

text

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