A search for double-electron capture of 74Se to excited levels using coincidence/anticoincidence gamma-ray spectrometry

Abstract

Evaluation of single, coincidence and anticoincidence gamma-ray spectrometry methods has been carried out with the aim to search for double-electron capture in 74 Se. This process is unique, because there is probability for transition to the 2 + excited state in 74 Ge (1204 keV), and de-excitation through two gammaquanta cascade with energies of 595.9 keV and 608.4 keV. Long-term measurements with anticosmic shielded HPGe spectrometer and the coincidence HPGe-NaI(Tl) spectrometer did not show any evidence for the double-electron capture in 74 Se. The best limit for the half-life of the double electron capture in 74 Se (both for the neutrinoless and two neutrino processes) was estimated to be >1.5·10 19 years.

Limit on the radiative neutrinoless double electron capture of $$^{36}$$ 36 Ar from GERDA Phase I

“…Several experiments including the latter established limits on both neutrino accompanied and neutrinoless double electron capture of different isotopes (see Refs. [10][11][12][13][14][15][16][17]). For some isotopes the possibility of a resonant enhancement of the 0νECEC decay has been predicted in case of mass degeneracy between the initial state and an excited final state [4,18].…”

Neutrinoless double-electron capture

“…≥ 1.7 × 10 16 HPGe γ spectrometry (Belli et al, 2011b) LL, 0 þ g.s. ≥ 3.1 × 10 16 HPGe γ spectrometry (Belli et al, 2011b) KN, 1,2 1326.9(5) ð−0.1 − þ0.3Þ AE 0.6 52.3 (KN 1 ) 7.0 × 10 8 LM, ð0; 1; 2Þ þ 1382.4(2) ð2.9 − 6.1Þ AE 0.5 ≥ 2.9 × 10 16 HPGe γ spectrometry (Belli et al, 2011b) 21.9 (L 1 M 1 ) 5.7 × 10 5 Ješkovský et al (2015) and reestimated as 3.9 × 10 16 yr by . See those works for details.…”

“…b The result 1.5 × 10 19 yr of Ješkovský et al (2015) for 74 Se was reestimated as 6.3 × 10 17 yr by .…”

“…The next search for a potentially resonant LL capture of 74 Se to the 1204 keV level of 74 Ge was realized in an experiment (Frekers et al, 2011) using HPGe γ spectrometry of a 3 kg Se sample with a limit T 1=2 ≥ 4.3 × 10 19 yr. However, this value was corrected to > 1.4 × 10 18 yr by Ješkovský et al (2015) and reevaluated as > 3.9 × 10 16 yr by because the method of setting the limit was not reliable enough. obtained the limit (Ješkovský et al, 2015) for the 0ν2EC transition of 74 Se to the 1204 keV excited level of 74 Ge, T 1=2 ≥ 1.5 × 10 19 yr with the help of HPGe γ spectrometry in coincidence with NaI(Tl) scintillation counter of the same selenium sample as in the experiment (Frekers et al, 2011).…”

“…However, this value was corrected to > 1.4 × 10 18 yr by Ješkovský et al (2015) and reevaluated as > 3.9 × 10 16 yr by because the method of setting the limit was not reliable enough. obtained the limit (Ješkovský et al, 2015) for the 0ν2EC transition of 74 Se to the 1204 keV excited level of 74 Ge, T 1=2 ≥ 1.5 × 10 19 yr with the help of HPGe γ spectrometry in coincidence with NaI(Tl) scintillation counter of the same selenium sample as in the experiment (Frekers et al, 2011). The limit was reevaluated as T 1=2 ≥ 6.3 × 10 17 yr for the same reason of a not quite correct interpretation of the experiment sensitivity as a half-life limit.…”