Observation of positronium annihilation in the 2S state: towards a new measurement of the 1S-2S transition frequency

D. A. Cooke, P. Crivelli, J. Alnis +8

We report the first observation of the annihilation of positronium from the 2S state. Positronium (Ps) is excited with a two-photon transition from the 1S to the 2S state where its…