Abstract
Using continuous-wave excitation to eliminate the problems inherent with pulsed laser measurements of nonlinear transitions, we have measured the interval in positronium (Ps) to be 1 233 607 216.4±3.2 MHz. The quoted 2.6 ppb (parts per ) uncertainty is primarily due to the determination of the Ps resonance relative to the reference line, with a 1.5 ppb contribution from a recent calibration of the line relative to the hydrogen 1S-2S transition. The uncertainty corresponds to 3.5× of the QED contribution to the interval. Our measurement is sufficiently accurate to provide a test of the as yet uncalculated QED corrections.
- Received 1 October 1992
DOI:https://doi.org/10.1103/PhysRevLett.70.1397
©1993 American Physical Society