Nuclear fission barriers, mass parameters and spontaneous fission half lives of fermium isotopes calculated in a framework of the Skyrme Hartree-Fock-Bogoliubov model with the SkM* force are discussed. Zero-point energy corrections in the ground state are determined for each nucleus using the Gaussian overlap approximation of the generator coordinate method and in the cranking formalism. Results of spontaneous fission half lives are compared to experimental data.
ForewordThe field of research of nuclear fission has been turned up more than 70 years ago as a result of the discovery of the process by O. Hahn and F. Strassman explained by L. Meitner and O. Frisch. 1 Since the time of the discovery there were proposed plenty of models explaining basic features of the fission. Yet, there is no uniform theory based on fundamental assumptions about nuclear forces which explains in a satisfactory way all of the peculiarities of this complex process of division of many body nuclear system into two fragments. One of the main features which is still a challenge is a variety of observed spontaneous fission half lives (SFHL) of heavy nuclei. The half lives of fermium isotopes can serve as an example.Experimentally known logarithmic dependence of SFHL of fermium nuclei on the mass or neutron number looks like an inverted parabola showing a maximum at A = 252 (see Figure 1). The shortest half-live time corresponds to the isotope A = 242 and the longest one to A = 252. The measured SFHL range approximately from 10 −4 s up to 10 9 s covering 12-13 decades. Spontaneous fission half lives vary fairly smoothly as one goes from Uranium to Fermium. However, at 258 Fm there is 557 Int. J. Mod. Phys. E 2011.20:557-564. Downloaded from www.worldscientific.com by UNIVERSITY AT BUFFALO on 03/03/15. For personal use only.