English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report on a series of 42 measurements of the transition frequency of the429~THz (5s$^2$)~$^1$S$_0$--(5s5p)~$^3$P$_0$ line in $^{87}$Sr taken over threeyears from 2017 to 2019. They have been performed at thePhysikalisch-Technische Bundesanstalt (PTB) between the laboratory strontiumlattice clock and the primary caesium fountain clocks CSF1 and CSF2. The lengthof each individual measurement run has been extended by use of a hydrogen maseras flywheel to improve the statistical uncertainty given by the Cs clocks. Wedetermine an averaged transition frequency of$429\:228\:004\:229\:873.00(0.07)$~Hz with $1.5\times10^{-16}$ fractionaluncertainty, at the limit of the current realization of the unit hertz.Analysis of the data provides an improved limit on the coupling of thegravitational potential of the Sun to the proton--electron mass ratio $\mu$,and confirms the limits on its temporal drift.

Long term measurement of the $^{87}$Sr clock frequency at the limit of primary Cs clocks