Probing the nuclide 180W for neutrinoless double-electron capture exploration

The mass difference of the nuclides W-180 and Hf-180 has been measured with the Penning-trap mass spectrometer SHIPTRAP to investigate W-180 as a possible candidate for the search for neutrinoless double-electron capture. The Q(epsilon epsilon)-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(+) -> 0(+) ground-state to ground-state double-electron capture transition of approximately 5 x 10(27) years/< m(epsilon epsilon)vertical bar eV vertical bar >(2). (C) 2011 Elsevier B.V. All rights reserved.