Probing the nuclide 180W for neutrinoless double-electron capture   exploration
  The mass difference of the nuclides 180W and 180Hf has been measured with the Penning-trap mass spectrometer SHIPTRAP to investigate 180W as a possible candidate for the search for neutrinoless doubleelectron capture. The Q-value was measured to 143.20(27)keV. This value in combination with the calculations of the atomic electron wave functions and other parameters results in a half-life of the 0+ \rightarrow 0+ ground-state to ground-state double-electron capture transition of approximately 5\cdot10E27 years/<m_ee[eV]>^2. 
C. Droese, K. Blaum, M. Block, S. Eliseev, F. Herfurth, E. Minaya   Ramirez, Yu. N. Novikov, L. Schweikhard, V. M. Shabaev, ...
nucl-ex