Speaker
Description
We report the results of a new measurement of the $2\,^3$S$_1 \rightarrow 2\,^1$P$_1$ transition ($\nu_F$) in positronium (Ps). Though this transition is forbidden by charge conjugation symmetry (C), it can be observed in a magnetic field. We optically excite Ps from a pulsed beam to produce radiatively metastable $2\,^3$S$_1$ atoms and drive them to the $2\,^3$P$_1$ level in a rectangular waveguide using microwave radiation. The C-allowed $2\,^3$S$_1 \rightarrow 2\,^3$P$_1$ transition ($\nu_1$) was also measured in the same waveguide, using the same techniques, and the observed Zeeman shift was used 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 |$\langle 2\,^1$P$_1|H_{{C}P} | 2\,^3$P$_1 \rangle$|
