Muon transfer from deuterium to helium

We report on an experiment at the Paul Scherrer Institute, Villigen, Switzerland measuring x rays from muon transfer from deuterium to helium. Both the ground-state transfer via the exotic (dμ3,4He)* molecules and the excited-state transfer from (μd)* were measured. The use of charge-coupled device detectors allowed x rays from 1.5 keV to 11 keV to be detected with sufficient energy resolution to separate the transitions to different final states in both deuterium and helium. The x-ray peaks of the (dμ3He)* and (dμ4He)* molecules were measured with good statistics. For the D2+3He mixture, the peak has its maximum at Edμ3He=6768±12 eV with full width at half maximum (FWHM) Γdμ3He=863±10 eV. Furthermore, the radiative branching ratio was found to be κdμ3He=0.301±0.061. For the D2+4He mixture, the maximum of the peak lies at Edμ4He=6831±8 eV and the FWHM is Γdμ4He=856±10 eV. The radiative branching ratio is κdμ4He=0.636±0.097. The excited-state transfer is limited by the probability to reach the deuterium ground state, q1s. This coefficient was determined for both mixtures: q1s3He=68.9±2.7% and q1s4He=90.1±1.5%