First Search for $2\Varepsilon $ and $\Varepsilon\Beta^+ $ Decay Of
First search for 2ε and εβ+ decay of 162Er and new limit on 2β− decay of 170Er to the first excited level of 170Yb P. Bellia, R. Bernabeia,b,1, R.S. Boikoc,d, F. Cappellae, V. Caracciolof , R. Cerullia, F.A. Danevichc, A. Incicchittie,g, B.N. Kropivyanskyc, M. Laubensteinf , S. Nisif , D.V. Podac,h, O.G. Polischukc, V.I. Tretyakc aINFN sezione Roma “Tor Vergata”, I-00133 Rome, Italy bDipartimento di Fisica, Universita` di Roma “Tor Vergata”, I-00133 Rome, Italy cInstitute for Nuclear Research, 03028 Kyiv, Ukraine dNational University of Life and Environmental Sciences of Ukraine, 03041 Kyiv, Ukraine eINFN sezione Roma, I-00185 Rome, Italy f INFN, Laboratori Nazionali del Gran Sasso, I-67100 Assergi (AQ), Italy gDipartimento di Fisica, Universita` di Roma “La Sapienza”, I-00185 Rome, Italy hCSNSM, Universit´eParis-Sud, CNRS/IN2P3, Universit´eParis-Saclay, 91405 Orsay, France Abstract The first search for double electron capture (2ε) and electron cap- arXiv:1808.01782v1 [nucl-ex] 6 Aug 2018 ture 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- 15 18 life limits were estimated at the level of lim T1/2 ∼ 10 − 10 yr. A 162 + possible resonant 0νKL1 capture in Er to the 2 1782.7 keV ex- 162 17 cited state of Dy is restricted as T1/2 ≥ 5.0 × 10 yr at 90% C.L.
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