  We show that the recent observation of the time modulation of two-body weak
decays of heavy ions reveals the mass content of the electron neutrinos via
interference patterns in the recoiling ion wave function. From the modulation
period we derive the difference of the square masses $ \Delta m^2\approx
22.5\times 10^{-5}$ eV${}^2$, which is about 2.8 times larger than that derived
from a combined analysis of KamLAND and solar neutrino oscillation experiments.
It is, however, compatible with a data regime to which the KamLAND analysis
attributes a smaller probability.
  The experimental results imply that the neutrino mixing matrix violates
unitarity by about 10%.
