Investigation of rare nuclear decays with BaF2 crystal scintillator contaminated by radium

The radioactive contamination of a BaF2 scintillation crystal with mass of 1.714 kg was measured over 101 hours in the low-background DAMA/RD however, its \( \beta\) decay is also energetically allowed with \( Q_{\beta}=24\pm 21\) keV. Search for decay chains of events with specific pulse shapes characteristic for \( \alpha\) or for \( \beta/\gamma\) signals and with known energies and time differences allowed us to set, for the first time, the limit on the branching ratio of 222Rn relatively to \( \beta\) decay as \( B_{\beta} 8.0\) y). The half-life limits of 212Pb, 222Rn and 226Ra relatively to 2\( \beta\) decays are also improved in comparison with the earlier results.