Rewriting the textbooks: Confusion over nuclear fission: "Last year, these ideas were put to the test at ISOLDE, a facility for making rare radioactive isotopes at CERN near Geneva, Switzerland, to predict the outcome of fissioning mercury-180. Dividing mercury-180 evenly gives two zirconium-90 nuclei, which just happen to have a magic number of neutrons and an almost magic number of protons. Given all that, says Phil Walker of the University of Surrey in Guildford, UK, to expect exactly that outcome is 'a no-brainer'.
Sadly, mercury-180 doesn't play by the rules. It divides asymmetrically into the distinctly unmagical nuclei ruthenium-100 and krypton-80 (Physical Review Letters, vol 105, p 252502).
'It's surprising that a process as basic as fission so obviously does not agree with what is expected,' says Walker."