Sw. Fan et al., HYPERFINE SPLITTING IN POSITRONIUM MEASURED THROUGH QUANTUM BEATS IN THE 3-GAMMA DECAY, Physics letters. A, 216(1-5), 1996, pp. 129-136
Quantum beat oscillations in the 3 gamma decay of the positronium atom
arising from interference between the different spin states have been
observed using a simple beta-start and gamma-stop detection system. M
easurements of the beat frequency at different magnetic fields have yi
elded a value of the 1 S-1(0)-1 S-3(1) hyperfine interaction of 202.5
+/- 3.5 GHz, in good agreement with previous measurements. This novel
approach does not require high magnetic fields and the use of microwav
e radiation to quench the triplet substate of the positronium atom.