Complete ground-state transition rates for the helium 2 P3 manifold

This work presents experimental measurements of the 2 P3 2 →1 S1 0 and 2 P3 0 →1 S1 0 transition rates for helium. It completes the determination of the decay rates to the ground state from the 2 P3 manifold and also completes the 2 P3 2 decay rates for the metastable rare-gas series. The rate of photon emission from the 2 P3 2 and 2 P3 0 states to the 1 S1 0 ground state is measured relative to the emission rate from the 2 P3 1 →1 S1 0 transition, which we have determined previously for the first time. The value for the 2 P3 2 →1 S1 0 transition is 0.324±0.016 s-1. An upper bound of □0.01 s-1 is placed on the emission rate for the 2 P3 0 →1 S1 0 transition, which is predicted to be strictly forbidden. Along with our previous measurement of the 2 S3 1 lifetime, the 2 P3 manifold decay rates are in excellent agreement with current quantum-electrodynamic theory.