Experimental searches for rare alpha and beta decays

The current status of the experimental searches for rare alpha and beta decays is reviewed. Several interesting observations of alpha and beta decays, previously unseen due to their large half-lives (10^15 − 10^20 yr), have been achieved during the last years thanks to the improvements in the experimental techniques and to the underground locations of experiments that allows to suppress backgrounds. In particular, the list includes first observations of alpha decays of 151Eu, 180W (both to the ground state of the daughter nuclei), 190Pt (to excited state of the daughter nucleus), 209Bi (to the ground and excited states of the daughter nucleus). The isotope 209Bi has the longest known half-life of T1/2 ≈ 10^19 yr relatively to alpha decay. The beta decay of 115In to the first excited state of 115Sn (Eexc = 497.334 keV), recently observed for the first time, has the Qβ value of only (147 ± 10) eV, which is the lowest Qβ value known to-date. Searches and investigations of other rare alpha and beta decays (48Ca, 50V, 96Zr, 113Cd, 123Te, 178m2Hf, 180mTa and others) are also discussed.