Speaker
Description
We report the results of a new measurement of the $2~^3 \mathrm{S}_1 \rightarrow 2~^1\mathrm{P}_1$ transition ($\nu_\mathrm{F}$) in positronium (Ps). This transition, which is strictly forbidden by charge conjugation symmetry (C), can be observed in a magnetic field. Using a pulsed Ps beam we optically generate radiatively metastable $2~^3\mathrm{S}_1$ atoms, and then drive them to the $2~^1\mathrm{P}_1$ level in a rectangular waveguide using microwave radiation. Using the same technique, we also measured the C-allowed $2~^3\mathrm{S}_1 \rightarrow 2~^3\mathrm{P}_1$ transition ($\nu_1$) in the same waveguide, and used the observed Zeeman shift to determine the local magnetic field strength. The measurements were performed in a range of magnetic fields, making it possible to determine the field-free $\nu_1$ and $\nu_F$ transition frequencies, and to set limits on the C-forbidden transition matrix element |⟨$2~^1 \mathrm{P}_1|H_{{C}{P}}|2~^3\mathrm{P}_1⟩|$.
