Comparative Study of Spontaneous-Fission Characteristics of 252No and 254No Isotopes

Spontaneous fissions of the 252No and 254No nobelium isotopes have been studied in a series of experiments with the SHELS separator. These isotopes are produced by colliding a beam of 48Ca ions from the U-400 cyclotron with the 206Pb and 208Pb targets. The measured characteristics of the 252No and 254No spontaneous fissions include their half-lives, total kinetic energies of fission fragments, and prompt-neutron multiplicities. The average number of neutrons per 254No spontaneous-fission act is measured for the first time as 4.88 ± 0.53.