A Search for various Double Beta Decay Modes of Cd, Te and Zn Isotopes

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Various double beta decay modes of Cd, Zn and Te isotopes are explored with the help of CdTe and CdZnTe semiconductor detectors. The data set is splitted in an energy range below 1 MeV having a statistics of 134.5 g and one above 1 MeV resulting in 532 g. No signals were observed in all channels under investigation. New improved limits for the neutrinoless double beta decay of Zn70 of T₁/₂ > 1.3 · 10¹⁶ yrs (90% CL), the longest standing limit of all double beta isotopes, and 0νβ+EC of Te120 of T₁/₂ > 2.2 · 10¹⁶ yrs (90% CL) are given. For the first time a limit on the half-life of the 2νECEC of ¹²⁰Te of T₁/₂ > 9.4 · 10¹⁵ yrs (90% CL) is obtained. In addition, limits on 2νECEC for ground state transitions of Cd106, Cd108 and Zn64 are improved. The obtained results even under rough background conditions show the reliability of CdTe semiconductor detectors for rare nuclear decay searches.