{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/direct-measurement-of-the-forbidden-2-3-s-1","title":"Direct Measurement of the Forbidden $2^{3\\!}S_1 \\rightarrow 3^{3\\!}S_1$ Atomic Transition in Helium","arxiv_id":"2002.04811","date":"2020-02-12","proceeding":null,"authors":["K. F. Thomas","J. A. Ross","B. M. Henson","D. K. Shin","K. G. H. Baldwin","S. S. Hodgman","A. G. Truscott"],"abstract":"We present the detection of the highly forbidden $2^{3\\!}S_1 \\rightarrow 3^{3\\!}S_1$ atomic transition in helium, the weakest transition observed in any neutral atom. Our measurements of the transition frequency, upper state lifetime, 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 ultracold metastable ($2^{3\\!}S_1$) helium atoms: low background direct detection of excited then decayed atoms for sensitive measurement of the transition frequency and lifetime; and a pulsed atom laser heating measurement for determining the transition strength. These methods could possibly be applied to other atoms, providing new tools in the search for ultra-weak transitions and precision metrology.","url_abs":"https://arxiv.org/abs/2002.04811v2","url_pdf":"https://arxiv.org/pdf/2002.04811v2.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"direct-measurement-of-the-forbidden-2-3-s-1","repo_url":"https://github.com/KF-Thomas/Forbidden_Transition","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}