Precision measurement of the 2p-1s transition wavelength in muonic 13C

Abstract With the bent-crystal spectrometer at the SIN muon channel we have measured the wavelength of the 2p-1s transition in muonic 13 C with a precision of 13 ppm. The result for the 2 p 3 2 -1 S 1 2 transition is λ(2 p 3 2 -1 s 1 2 ) = 16.46055 ± 0.00021 pm ; it is interpreted in terms of a short-range muon-nucleon interaction not included in standard QED calculations.