Positronium ground state decay rate

Studies of the positronium atom have been previously limited to measurements of the ground state decay rates[8], and microwave studies of the n=l "hyperfine"[9,10] I Sq - interval, and a... 

In Chapter 1, the first order contributions to the annihilation rates from the dominant modes of decay of the S-states of both ortho- and para-positronium (for arbitrary principal quantum number nPs) were given as equations (1.5) and (1.6). These contributions are included in the following equations for the rates for the two ground states, which also contain terms of higher order in the fine structure constant, a ... 

Precision redetermination of the fine-structure interval of the ground state of positronium and a direct measurement of the decay rate of parapositronium. Phys. Rev. A 2 707-721. 

Abstract. The current experimental situation regarding tests of fundamental physics using positronium is reviewed. Five measurements are discussed and compared with theoretical predictions the singlet and triplet annihilation decay rates, the ground state and the n = 2 energy intervals, and the Doppler-free two-photon excitation of the IS to 2S transition. Previous results, recent progress (where appropriate), and the outlook for future improvements in these measurements are discussed. 

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