Superallowed α Decay to Doubly Magic 100Sn

We report the first observation of the Xe-108 -> Te-104 -> Sn-100 alpha-decay chain. The alpha emitters, Xe-108 [E-alpha = 4.4(2) MeV, T-1/2 = 58(-23)(+106) mu s] and Te-104[E-alpha = 4.9(2) MeV, T-1/2 < 18 ns], decaying into doubly magic(100)Sn were produced using a fusion-evaporation reaction Fe-54(Ni-58, 4n)Xe-108, and identified with a recoil mass separator and an implantation-decay correlation technique. This is the first time alpha radioactivity has been observed to a heavy self-conjugate nucleus. A previous benchmark for study of this fundamental decay mode has been the decay of Po-212 into doubly magic Pb-208. Enhanced proton-neutron interactions in the N = Z parent nuclei may result in superallowed a decays with reduced a-decay widths significantly greater than that for Po-212. From the decay chain, we deduce that the a-reduced width for Xe-108 or Te-104 is more than a factor of 5 larger than that for Po-212.