Search For Double Electron Capture Research Articles

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

The first search for double electron capture (2ε) and electron capture with positron emission (εβ+) of 162Er to the ground state and to several excited levels of 162Dy was realized with 326 g of highly purified erbium oxide. The sample was measured over 1934 h by the ultra-low background HP Ge γ spectrometer GeCris (465 cm3) at the Gran Sasso underground laboratory. No effect was observed, the half-life limits were estimated at the level of yr. A possible resonant 0ν KL1 capture in 162Er to the 2+ 1 782.7 keV excited state of 162Dy is restricted as T1/2 ≥ 5.0 × 1017 yr at 90% C.L. A new improved half-life limit T1/2 ≥ 4.1 × 1017 yr was set on the 2β− decay of 170Er to the 2+ 84.3 keV first excited state of 170Yb.

New limits on $2 \varepsilon$ 2 ɛ , $\varepsilon \beta^{+}$ ɛ β + and $2 \beta^{+}$ 2 β + decay of 136Ce and 138Ce with deeply purified cerium sample

A search for double electron capture ($2\varepsilon$), electron capture with positron emission ($\varepsilon\beta^+$), and double positron emission $2\beta^+$) in $^{136}$Ce and $^{138}$Ce was realized with a 465 cm$^3$ ultra-low background HP Ge $\gamma$ spectrometer over 2299 h at the Gran Sasso underground laboratory. A 627 g sample of cerium oxide deeply purified by liquid-liquid extraction method was used as a source of $\gamma$ quanta expected in double $\beta$ decay of the cerium isotopes. New improved half-life limits were set on different modes and channels of double $\beta$ decay of $^{136}$Ce and $^{138}$Ce at the level of $T_{1/2}>10^{17}-10^{18}$ yr.

New search for double electron capture in 106Cd decay with the TGV-2 spectrometer

A new experiment devoted to searches for double electron capture in 106Cd decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The limit T 1/2(2νEC/EC) > 2.0×1020 yr at a 90%confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope 106Cd to 99.57%. The limits T 1/2(KL, 2741 keV) > 0.9 × 1020 yr and T 1/2(KK, 2718 keV) ≫ 1.4 × 1020 yr at a 90% C.L. on the neutrinoless decay of 106Cd were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope 106Cd.