Dall, RobertByron, LesaTruscott, AndrewBaldwin, Kenneth2009-09-162010-12-202009-09-162010-12-2015/01/2008Physical Review Letters 100.2 (2008): 023001/1-40031-9007 1079-7114http://hdl.handle.net/10440/855We present the first experimental determination of the 2 3P1–1 1S0 transition rate in helium and compare this measurement with theoretical quantum-electrodynamic predictions. The experiment exploits the very long (∼1 minute) confinement times obtained for atoms magneto-optically trapped in an apparatus used to create a Bose-Einstein condensate of metastable (2 3S1) helium. The 2 3P1–1 1S0 transition rate is measured directly from the decay rate of the cold atomic cloud following 1083 nm laser excitation from the 2 3S1 to the 2 3P1 state, and from accurate knowledge of the 2 3P1 population. The value obtained is 177±8 s-1, which agrees very well with theoretical predictions, and has an accuracy that compares favorably with measurements for the same transition in heliumlike ions higher in the isoelectronic sequence.4 pagesapplication/pdfen-AUThe American Physical SocietyKeywords: Electrodynamics; Metastable phases; Quantum electronics; Transition metals; Experimental determination; Isoelectronic sequence; HeliumExperimental determination of the helium 2 3P1-1 1S0 transition rate2008PhysRevLett.100.0230012015-12-09