Double resonant enhancement in the neutrinoless double-electron capture ofPt190

Abstract

Background: The observation of neutrinoless double-beta transitions would indicate physics beyond the standard model as the lepton number conservation is violated. For a complete degeneracy in the energy of the initial and final states, the neutrinoless double-electron capture is resonantly enhanced. This shortens the half-life to similar orders of magnitude as the neutrinoless double-beta decay and expands the set of nuclei for the search of neutrinoless double-beta transitions as the observation of either process would be equally likely. Purpose: In order to clearly identify transitions that are resonantly enhanced, among other parameters the total energy of the decay, Qεε, needs to be measured very precisely. Of the twelve initially identified candidates, the last remaining decay without a precise Qεε was 190 Pt(0νεε) 190 Os. Method: The Qεε value was determined with the Penning trap mass spectrometer LEBIT by measuring the ratio of the cyclotron frequencies of 190 Pt + and 190 Os + in a 9.4 T superconducting magnet. Result: The Qεε value was determined to be 1401.57(47) keV with an uncertainty reduction of an order of magnitude compared to its previously known value. The absolute value is shifted by 17.17(623) keV relative to the previously accepted one. Furthermore, the mass value of 190 Pt was found to be shifted by more than three standard deviations. In addition we improved the mass values for 186,190 Os, 194 Pt. Conclusion: Transitions to the two nuclear excited states of 190 Os with 1326.9(5) keV and 1387.00(2) keV energy were identified to be resonantly enhanced within a 1σ uncertainty. The significantly reduced uncertainty of Qεε confirmed the potential for a resonantly enhanced transition.

β -decay Q values among the A=50 Ti-V-Cr isobaric triplet and atomic masses of Ti<

“…However, offline sources, including a plasma source and a recently commissioned laser ablation source (LAS) [14] enable access to a wide range of stable and long-lived isotopes. Ions from these sources are used for calibration purposes and for mass and Q value determinations with applications, for example, in nuclear and neutrino physics [11,[15][16][17][18][19][20]. A schematic diagram of the sections of the LEBIT facility used in this work is shown in Fig.…”

Direct determination of the La138β -decay Q value using Penning trap mass spectrometry

“…LEBIT was designed for online measurements of rare isotopes from the Coupled Cyclotron Facility, but also houses two offline sources-a laser ablation source (LAS) [34] and a plasma ion source-that can be used for the production of stable and long-lived isotopes. These offline sources provide reference ions during rare isotope measurements, but also provide access to a wide range of isotopes that have been used for studies related to neutrinoless double β-decay [35][36][37][38][39][40], highly forbidden β-decays [7,8], and ultra-low Q value β-decays [41].…”

First search for 2ε and εβ + decay of 162Er and new limit on 2β − decay of 170Er to the first excited level of 170Yb

“…Taking into account that the sensitivity of the most recent 0ν2β − experiments is almost one order magnitude higher (e.g., the KamLAND-Zen experiment already reached an effective Majorana neutrino mass sensitivity ñ ⟨ ⟩ m lim 0.1 eV [15]) the corresponding theoretical half-life for 164 Er is on the level of ∼10 32 yr. Nevertheless, despite the precision mass measurements indicate that the actually most promising double electron capture candidates are 152 Gd, 156 Dy and 190 Pt [34][35][36], 164 Er remains an interesting nucleus in the list of resonant neutrinoless double electron capture candidates. So that was the reason to investigate the radiopurity level of erbium, and to estimate the possibilities of erbium purification from radioactive elements.…”