Precision Microwave Spectroscopy of the Positronium 2 S 3 1 →2 P 3 2 Interval

Abstract

We report the results of a new measurement of the positronium 2 S31→2 P32 (ν2) interval. Using a modified experimental arrangement we have significantly reduced the effects of microwave reflections, which in previous experiments resulted in shifts and asymmetric line shapes. With the improved apparatus we obtain an experimental value of ν2=8627.94±0.95 MHz, which is within 1.3σ of the theoretical value 8626.71±0.08 MHz.