Measurement of the Lamb shift in the n = 2 state of muonium

We report the results of a measurement of the Lamb shift in the {ital n}=2 state of muonium. Muonium atoms in the metastable 2{ital S} state were produced by the beam-foil method and the formation rate was determined by observation of the Ly-{alpha} photons emitted when the metastable atoms were quenched in a static electric field. The Lamb shift ({ital scrS}{sub Mu}) was measured through observation of the microwave-induced 2 {sup 2}S{sub 1/2}--2 {sup 2}P{sub 1/2} transition with the result {ital scrS}{sub Mu}=1042{sub {minus}23}{sup +21} MHz. This result is in agreement with the current theoretical value.