Can Chemical Environment Affect Nuclear Properties?

A new experiment shows that the decay lifetime of radioactive beryllium-7 changes by almost 1% when placed inside a carbon-60 molecule. This is perhaps the largest shift yet seen in a chemically induced modification of a nuclear lifetime. The Be-7 is unstable and one way for it to decay is for the nucleus to capture one of its own electrons, process in which a proton is turned into a neutron.

Now if the Be atom lies in the cavity within a C₆₀ molecule (in which case it is referred to as endohedral Be, or abbreviated further, Be@C₆₀) the surrounding halo of carbon-based electrons apparently modifies the wave-functions of the beryllium-associated electrons and the associated "phase space" so that the rate at which electrons are captured by the Be nucleus is speeded up.

Previous attempts to modify nuclear lifetimes through chemical means have resulted in shifts that were at the 0.15% level. The researchers from Tohoku University and Yokohama National University (Japan) doing the present experiment believe that it would be premature to suggest that this approach can be used to mitigate the problems of storing radioactive materials, but, in the near term the use of endohedral fullerenes (cargo-carrying C₆₀ molecules) might lead to specialized radio-therapies or tracers for tagging metabolic pathways in the body. (Ohtsuki et al., Physical Review Letters, 10 September 2004; Ohtsuki@LNS.tohoku.ac.jp)