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.
@article{arxiv.1209.5174,
title = {Q value and half-life of double-electron capture in Os-184},
author = {C. Smorra and T. R. Rodriguez and T. Beyer and K. Blaum and M. Block and Ch. E. Düllmann and K. Eberhardt and M. Eibach and S. Eliseev and K. Langanke and G. Martinez-Pinedo and Sz. Nagy and W. Nörtershäuser and D. Renisch and V. M. Shabaev and I. I. Tupitsyn and N. A. Zubova},
journal= {arXiv preprint arXiv:1209.5174},
year = {2012}
}