News on radioactive decay

Very rare 14C-decay modes were first observed for the 14C-emission from 223Ra: natural 14C-radioactivity having a 14C-to-α branching ratio of about 5.10-10. The 24Ne-emission from 232U, the second decay mode of this class has a probability which is smaller by about two orders of magnitude. New results were also observed for the emission of multiple and uncommon particles after β-decay. The β-delayed emission of one proton or up to two neutrons is a common process known for about 50 or 100 nuclides, respectively. The β-delayed two-proton emission, however, was first detected for the short-lived nuclides 22Al and 26P.11Li (tsub(1/2)=8.6 ms) is an unique radionuclide due to its totally six different decay modes. It is not only the first nuclide to emit three neutrons after β--decay but also tritium nuclei as a rare event (about 10-2 %). The 3n-radioactivity is remarkable to the fact that due to instable 8Be this decay results in the (not resolved by time) emission of five particles: 11Lisup(β-)->2α+3n. Beta-delayed fission of heavy nuclides is known for both neutron and proton rich nuclides and reaches probabilities near 100% for very heavy neutron rich nuclides. This kind of decay is the limiting factor for built-up of heavy transuranium elements by making use of underground nuclear explosion experimental limits are A=257 and Z=100. It also seems to be responsible for the limit of formation of heaviest nuclides in the stellar neutron capture process (r-process). (orig.)