  The atomic mass difference of 163Ho and 163Dy has been directly measured with
the Penning trap mass spectrometer SHIPTRAP applying the novel phase imaging
ion cyclotron resonance technique. Our measurement has solved the long standing
problem of large discrepancies in the Q value of the electron capture in 163Ho
determined by different techniques. Our measured mass difference shifts the
current Q value of 2555(16) eV evaluated in the Atomic Mass Evaluation 2012 [G.
Audi et al., Chin. Phys. C 36, 1157 (2012)] by more than 7 sigma to
2833(30stat)(15sys) eV/c2. With the new mass difference it will be possible,
e.g., to reach in the first phase of the ECHo experiment a statistical
sensitivity to the neutrino mass below 10 eV, which will reduce its present
upper limit by more than an order of magnitude.
