Q value and half-life of double-electron capture in Os-184
  Os-184 has been excluded as a promising candidate for the search of neutrinoless double-electron capture. High-precision mass measurements with the Penning-trap mass spectrometer TRIGA-TRAP resulted in a marginal resonant enhancement with = -8.89(58) keV excess energy to the 1322.152(22) keV 0+ excited state in W-184. State-of-the-art energy density functional calculations are applied for the evaluation of the nuclear matrix elements to the excited states predicting a strong suppression due to the large deformation of mother and daughter states. The half-life of the transition in Os-184 exceeds T_{1/2} > 1.3 10^{29} years for an effective neutrino mass of 1 eV. 
C. Smorra, T. R. Rodriguez, T. Beyer, K. Blaum, M. Block, Ch.E.   D\"ullmann, K. Eberhardt, M. Eibach, S. Eliseev, K. Langan...
nucl-ex