Measurement of cold fission for 229Th(nth,f), 232U(nth,f) and 239Pu(nth,f) with the Cosi fan tutte spectrometer

The light-fragment-group mass-energy correlations for 229Th(nth, f), 232U(nth, f) and 239Pu(Nth, f) measured with the Cosi fan tutte, have been used to determine the cold fission probability for these fissioning systems. These are the first results on cold fission for 229Th(nth, f) and 232U(nth, f). For 229Th(nth, f) cold fission is realised for the whole mass range ML∼80-99 present in the mass spectrum, but the coldest fission shows up for ML∼85. For 232U(nth, f) cold fission is present for ML∼84-107, with the coldest fission manifesting for ML∼100-105. In the case of 239Pu(nth, f), cold fission exists for ML∼95-112 and here the coldest fission is produced for ML∼105-110. This systematic study shows that the shells in the nascent fragments seem to play a decisive role in the realisation of cold fission. These results are discussed in terms of the existing concepts and ideas on this phenomenon. (orig.)