Direct Q-Value Determination Of The Beta(-) Decay Of Re-187

The cyclotron frequency ratio of Os-187(29+) to Re-187(29+) ions was measured with the Penning-trap mass spectrometer PENTATRAP. The achieved result of R = 1.000 000 013 882(5) is to date the most precise such measurement performed on ions. Furthermore, the total binding-energy difference of the 29 missing electrons in Re and Os was calculated by relativistic multiconfiguration methods, yielding the value of Delta E = 53.5(10) eV. Finally, using the achieved results, the mass difference between neutral 187Re and Os-187, i.e., the Q value of the beta(-) decay of Re-187, is determined to be 2470.9(13) eV.