DAMA/NaI results for spontaneous emission of heavy clusters in 127I

The spontaneous emission of nuclear fragments heavier than α particles and lighter than the most probable fission fragments, named cluster decay, was theoretically predicted in 1980 and experimentally observed for the first time in 1984. Up to date, spontaneous emission of clusters ranging from 14C to 34Si from near twenty translead nuclei (from 221Fr to 242Cm) has been observed with branching ratios relative to α decay from 10-9 down to 10-16 and partial half-lives from 3.2 × 103 y up to 1.2 × 1020 y.

A new region of parent nuclei, for which cluster radioactivity can experimentally be observed, was recently predicted. These are the nuclei with Z=56-64 and N=58-72; daughter nuclei are close to double magic 10050Sn nuclide.

2005 - Thus, DAMA/NaI has searched for possible cluster decays of 127I considering an exposure of 33834 kg × day by searching for the energy released in the initial decay and subsequent decays of radioactive daughter nuclei. In those cases when the initial or intermediate decay has too long lifetime, only subsequent decays of radioactive daughter nuclei have been looked for. New limits have been obtained for possible cluster radioactivity in 127I, as reported in the following table.