Experiments to produce isotopes of superheavy elements with atomic numbers 114–116 in 48Ca ion reactions

Gas chemical properties of heaviest elements

“…Already back in the middle of the 1970 th search experiments were conducted both at FLNR in Dubna and at LBNL in Berkeley using this strategy [16,17]. Later, this approach was tried again several times with novel experimental setups that enabled search experiments with improved sensitivity [18].…”

Spontaneous fission half-life-times of double-odd nuclei (Z≧97)

“…It is well known that spontaneous fission half life times (SFHLT) of odd-odd nuclei are some orders of magnitude larger than corresponding values of neighbouring even-even nuclei with the mass number A smaller by two. In many experimental papers [1][2][3][4][5][6] these so called hindrance factors for odd-odd nuclei were arbitrarily assumed to be the same for each nucleus. However, calculations show a strong dependence on a nucleus chosen and they are equal to 5-7 orders of magnitude for light nuclei (Z_<_ 101) and 1-3 orders of magnitude for heavier actinides (Z> 103).…”

The Search for Superheavy Elements

“…6 where upper limits for the production cross sections are plotted as a function of the lifetimes covered by a given experimental technique. The Dubna group [55] used two different chemical separation schemes followed by spontaneous fission (SF) and aparticle counting (a), denoted by D in Fig. 6.…”

“…This reaction represents the intriguing case in which both the fusion probability and the survivability have been considered favourable. Projectile and target nucleus were brought together [55,28,[66][67][68] with an energy exceeding the barrier by about 20 MeV. The extra energy was thought to be necessary to induce complete fusion to produce a compound nucleus with some 40 MeV of excitation energy which is expected to de-excite by the evaporation of 4 neutrons.…”

“…Both in Berkeley [28,[66][67][68] and at Dubna [55] on the basis of some indirect hints for entrance channel limitations in heavy-ion fusion reactions [53] it was decided that some tens of MeV of extra push had to be provided to fuse 48 Ca with 248 Cm so that the compound system was formed with excitation energies between 34 and 54 MeV, which probably reduced their overall survival rates to hopelessly small values [53]. Today, in view of the results of the recent high-precision and highsensitivity fusion studies mentioned above, we conclude that this decision was wrong.…”