First millimeter-wave spectroscopy of ground-state positronium
First millimeter-wave spectroscopy of ground-state positronium
We report on the first measurement of the Breit–Wigner resonance of the transition from ortho-positronium to para-positronium. We have developed an optical system to accumulate a power of over 20 kW using a frequency-tunable gyrotron and a Fabry–Pérot cavity. This system opens a new era of millimeter-wave spectroscopy, and enables …