Investigation of the $\beta \beta$ decay of $^{96}$Zr to excited states in $^{96}$Mo
Résumé
The two-neutrino mode of double beta decay ($2νββ$) of $^{96}$Zr is investigated both theoretically and experimentally. The calculations, using the quasiparticle random phase approximation approach, show that for $^{96}$Zr the detection of 2νββ transitions to the two first excited states in the daughter nuclide will be possible in the very near future. On the experimental side, new, most stringent limits on half-lives for the double beta decay of $^{96}$Zr to excited states in $^{96}$Mo have been obtained with a 430 cm$^3$ ‘well-type’ germanium detector. They range between 5 × 10$^{19}$ and 8 × 10$^{19}$ years (90% CL)