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 of 74 Se to excited states. 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 gamma-quanta cascade with energies of 595.9 keV and 608.4 keV. Long-term measurements with an anticosmic shielded HPGe (high purity Ge) spectrometer and a 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 yr.