SPECTROSCOPY OF THE 1S-2S ENERGY SPLITTING IN MUONIUM

A new measurement of the 1(2)S(1/2)-2(2)S(1/2) energy splitting in muo nium (mu(+)e(-)) by Doppler-free two-photon laser spectroscopy yields a value of 2 455 529 002 (33) (46) MHz, where the 33 MHz error arises from statistics and the 46 MHz uncertainty is due to systematic line s hifts. The experiment agrees with quantum electrodynamics theory withi n two standard deviations. The mass of the positive muon can be derive d as 105.65880 (29) (43) MeV/c(2) from the measured muonium-hydrogen a nd muonium-deuterium 1S-2S isotope shifts. The measurement may alterna tively be interpreted as a test of the equality of the electric charge s of muon and electron with a precision of 1.4 (1.2).10 {-8}.