Experimental determination of the helium 2 3P1-1 1S0 transition rate

Abstract

We 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.