Seminarium Struktura Jądra Atomowego

I report on time-modulated two-body beta decays observed in the orbital electron capture of hydrogen-like Pr-140 and Pm-142 ions coasting in the ion storage ring of GSI. Using single-ion, time-resolved Schottky mass spectrometry it was found that the expected exponential decay is periodically modulated with a period of about 7 seconds for both systems. Tentatively, our observations are attributed to the coherent superposition of finite mass eigenstates of the electron neutrino generated in these two-body weak decays. Our experimental approach excludes to a large extent any systematical errors. On the other hand, the statistical significance of our data is still rather modest. Therefore, our findings still are very preliminary and have to be corroborated or disproved by additional experiments on other suitable two-body weak decays.