No abstract available

[en] The new isotope 12.3-minute ²⁵⁶Cf was produced via the (t,p) reaction on a ²⁵⁴Cf target, and a new 43-minute isomer of ²⁵⁸Md was produced via the (α,n) reaction on ²⁵⁵Es at the Los Alamos FN Tandem Van de Graaff facility. The mass and total kinetic energy distributions of the fission fragments from the spontaneous fission (SF) of the ²⁵⁶Cf were found to be very similar to those from SF of the lighter californium isotopes. The most probable total kinetic energy was nearly the same as that measured for ²⁵²Cf and ²⁵⁴Cf. The 43-minute ²⁵⁸Md decays by electron capture to 380-μs ²⁵⁸Fm, and therefore, we were able to study the mass and kinetic energy distributions from spontaneous fission of ²⁵⁸Fm. the mass distribution was narrowly symmetric, similar to that measured for ²⁵⁹Fm (SF), but much narrower than that reported for ²⁵⁷Fm (SF). The most probable total kinetic energy for ²⁵⁸Fm (SF) was measured to be 238 MeV, nearly as high as that of 243 MeV measured for ²⁵⁹Fm (SF), and much higher than the value of 198 MeV reported for ²⁵⁷Fm (SF). Thus, although a rather dramatic change in spontaneous fission properties occurs for fermium isotopes at N = 158, no such abrupt change was observed for the californium isotopes

[en] Published in summary form only

No abstract available

No abstract available

[en] A 1.5-sec spontaneous fission activity was produced by irradiation of ²⁵⁷Fm with 16-MeV tritons at the Los Alamos Tandem Van de Graaff Facility. On the basis of cross section and fission systematics, this 1.5-sec activity was attributed to ²⁵⁹Fm formed by the reaction, ²⁵⁷Fm(t,p)²⁵⁹Fm. ²⁵⁹Fm is the heaviest known isotope of fermium and has more neutrons than any other isotope so far identified. The mass distribution of the ²⁵⁹Fm is highly symmetric and the average total kinetic energy is very high, 230 +- 2 MeV. These features continue the trend toward more symmetric mass distributions and higher total kinetic energies observed previously for the fermium isotopes as the number of neutrons is increased

[en] We propose a new method to extract the collective masses and momenta associated with a given set of collective coordinates, along a dynamical microscopic mean-field evolution. We apply our method to the symmetric fission of ²⁵⁸Fm nucleus, and analyze the dynamical evolution of the system in the collective space. We compare, between the dynamical and the adiabatic paths, the force acting on the quadrupole degree of freedom, which is closely related to the relative distance between fragments. It is shown that dynamical effects beyond the adiabatic limit are important for formation and scission of the neck between emitted fragments. (authors)

[en] Possible errors in calculation of T_sf of atomic nuclei are discussed. The method of improving the results are briefly presented. (author). 1 refs, 4 figs

No abstract available

No abstract available