Coulomb effects in isobaric cold fission from reactions $^{233}$U($n_{\rm{th}}$,f), $^{235}$U($n_{\rm{th}}$,f), ${}^{239}$Pu($n_{\rm{th}}$,f) and $^{252}$Cf(sf)

Abstract

The Coulomb effect hypothesis, formerly used to interpret fluctuations in the curve of maximal total kinetic energy as a function of light fragment mass in reactions $^{233}$U($n_{\rm{th}}$,f), $^{235}$U($n_{\rm{th}}$,f) and $^{239}$Pu($n_{\rm{th}}$,f), is confirmed in high kinetic energy as well as in low excitation energy windows, respectively. Data from reactions $^{233}$U($n_{\rm{th}}$,f), $^{235}$U($n_{\rm{th}}$,f), ${}^{239}$Pu($n_{\rm{th}}$,f) and $^{252}$Cf(sf) show that, between two isobaric fragmentations with similar $Q$-values, the more asymmetric charge split reaches the higher value of total kinetic energy. Moreover, in low excitation energy windows, between two isobaric charge splits with different $Q$-values, the more asymmetrical fragmentations is preferred.