# Bound-state double-$\beta$ decay

Babič, A. (Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, 115 19 Prague, Czech Republic) (Institute of Experimental and Applied Physics, Czech Technical University in Prague, 128 00 Prague, Czech Republic) (Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia) ; Štefánik, D. (Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, 842 48 Bratislava, Slovakia) ; Krivoruchenko, M.I. (Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia) (Institute for Theoretical and Experimental Physics, 117259 Moscow, Russia) ; Šimkovic, F. (Institute of Experimental and Applied Physics, Czech Technical University in Prague, 128 00 Prague, Czech Republic) (Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia) (Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, 842 48 Bratislava, Slovakia)

06 December 2018

Abstract: We consider alternative modes of two-neutrino and neutrinoless double-$\beta$ decays in which one $\beta$ electron goes over to a continuous spectrum and the other occupies a vacant bound level of the daughter ion. We calculate the corresponding phase-space factors of the final states, estimate the partial decay rates, and derive the one- and two-electron energy spectra using relativistic many-electron wave functions of atoms provided by the multiconfiguration Dirac-Hartree-Fock package Grasp2K. While the bound-state neutrinoless double-$\beta$ decays are strongly suppressed, their two-neutrino counterparts can be observed in the next-generation double-$\beta$-decay experiments, most notably SuperNEMO.

Published in: Physical Review C 98 (2018)