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 present the detection of the highly forbidden $2^{3\!}S_1 \rightarrow3^{3\!}S_1$ atomic transition in helium, the weakest transition observed in anyneutral atom. Our measurements of the transition frequency, upper statelifetime, and transition strength agree well with published theoretical values,and can lead to tests of both QED contributions and different QED frameworks.To measure such a weak transition, we developed two methods using ultracoldmetastable ($2^{3\!}S_1$) helium atoms: low background direct detection ofexcited then decayed atoms for sensitive measurement of the transitionfrequency and lifetime; and a pulsed atom laser heating measurement fordetermining the transition strength. These methods could possibly be applied toother atoms, providing new tools in the search for ultra-weak transitions andprecision metrology.

Direct Measurement of the Forbidden $2^{3\!}S_1 \rightarrow 3^{3\!}S_1$ Atomic Transition in Helium