Observation of Non-Exponential Orbital Electron Capture Decays of Hydrogen-Like 140Pr and 142Pm Ions

Monday 3 Mar 2008, 15:30 → 17:00 Europe/Zurich

TH Theory Conference Room (CERN)

We report on the observation of time-modulated two-body weak decays in the orbital electron capture of hydrogen-like 140Pr58+ and 142Pm60+ ions coasting in the ion storage-cooler ring ESR at GSI. Using non-destructive single ion, time-resolved Schottky mass spectrometry we found that the expected exponential decay is periodically modulated in time with an oscillation period of about 7 seconds for both systems. We tentatively attribute our observations to the coherent superposition of finite mass eigenstates of the electron neutrino generated in these two-body weak decays.