Measurement of the 2S12−2P12 splitting in the (μ−4He)+ muonic ion

Abstract The measurement of the 2S 1 2 → 2P 1 2 energy transition in muonic helium is presented. The energy difference S 1 is found to be S exp 1 = 1381.3±0.5 meV. This result agrees with the expected value S 1 = 1381.2±0.3 meV obtained assuming the previously measured value for the 2S 1 2 → 2P 3 2 energy difference.