The 1s-2s energy interval in the muonium (渭+e-) atom has been measured by Doppler-free two-photon laser spectroscopy. A value of 2 455 528 941.0(9.8) MHz has been obtained in good agreement with quantum electrodynamics (QED). The muon-electron mass ratio can be extracted and is found to be 296.768 38(17). The measurement may also be interpreted as a determination of the muon-electron charge ratio as - 1 - 1.1(2.1)路10-9. Corresponding measurements in deuterium using the same experimental setup confirmed the validity of the applied analysis procedure
