The ground state to ground state electron-capture <math display="inline"><mi>Q</mi></math> value of <math display="inline"><mrow><mmultiscripts><mrow><mi>Dy</mi></mrow><mprescripts/><none/><mrow><mn>159</mn></mrow></mmultiscripts></mrow></math> (<math display="inline"><mn>3</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>-</mo></msup></math>) has been measured directly using the double Penning trap mass spectrometer JYFLTRAP. A value of 364.73(19) keV was obtained from a measurement of the cyclotron frequency ratio of the decay parent <math display="inline"><mrow><mmultiscripts><mrow><mi>Dy</mi></mrow><mprescripts/><none/><mrow><mn>159</mn></mrow></mmultiscripts></mrow></math> and the decay daughter <math display="inline"><mrow><mmultiscripts><mrow><mi>Tb</mi></mrow><mprescripts/><none/><mrow><mn>159</mn></mrow></mmultiscripts></mrow></math> ions using the novel phase-imaging ion-cyclotron resonance technique. The <math display="inline"><mi>Q</mi></math> values for allowed Gamow-Teller transition to <math display="inline"><mn>5</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>-</mo></msup></math> and the third-forbidden unique transition to <math display="inline"><mn>11</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>+</mo></msup></math> state with excitation energies of 363.5449(14) keV and 362.050(40) keV in <math display="inline"><mrow><mmultiscripts><mrow><mi>Tb</mi></mrow><mprescripts/><none/><mrow><mn>159</mn></mrow></mmultiscripts></mrow></math> were determined to be 1.18(19) keV and 2.68(19) keV, respectively. The high-precision <math display="inline"><mi>Q</mi></math> value of transition <math display="inline"><mn>3</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>-</mo></msup><mo stretchy="false">→</mo><mn>5</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>-</mo></msup></math> from this work, revealing itself as the lowest electron-capture <math display="inline"><mi>Q</mi></math> value, is used to unambiguously characterize all the possible lines that are present in its electron-capture spectrum. We performed atomic many-body calculations for both transitions to determine electron-capture probabilities from various atomic orbitals and found an order of magnitude enhancement in the event rates near the end point of energy spectrum in the transition to the <math display="inline"><mn>5</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>-</mo></msup></math> nuclear excited state, which can become very interesting once the experimental challenges of identifying decays into excited states are overcome. The transition to the <math display="inline"><mn>11</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>+</mo></msup></math> state is strongly suppressed and found unsuitable for measuring the neutrino mass. These results show that the electron-capture in the <math display="inline"><mrow><mmultiscripts><mrow><mi>Dy</mi></mrow><mprescripts/><none/><mrow><mn>159</mn></mrow></mmultiscripts></mrow></math> atom, going to the <math display="inline"><mn>5</mn><mo stretchy="false">/</mo><msup><mn>2</mn><mo>-</mo></msup></math> state of the <math display="inline"><mrow><mmultiscripts><mrow><mi>Tb</mi></mrow><mprescripts/><none/><mrow><mn>159</mn></mrow></mmultiscripts></mrow></math> nucleus, is a new candidate that may open the way to determine the electron-neutrino mass in the sub-eV region by studying electron-capture. Further experimental feasibility studies, including coincidence measurements with realistic detectors, will be of great interest.< Leer menos