Speaker
Description
The $^{238}$U($^{54}$Cr,4n)$^{288}$Lv and $^{242}$Pu($^{50}$Ti,3-4n)$^{288,289}$Lv reactions have been studied at the gas-filled separator DGFRS-2 at the SHE Factory at Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. Three new isotopes were discovered: two α-decaying nuclei $^{288}$Lv with α-particle energy E$_{α}$ = 11.08 MeV and half-life T$_{1/2}$ = 2.0 ms, $^{289}$Lv with E$_{α}$ = 10.90 MeV, T$_{1/2}$ = 2.4 ms, and granddaughter of $^{288}$Lv, spontaneously fissioning $^{280}$Cn with T$_{1/2}$ = 10 μs, which was observed after the first registration of α decay of $^{284}$Fl with E$_{α}$ = 10.57 MeV. Besides, for the first time we reliably registered the pxn channel of the $^{242}$Pu + $^{50}$Ti reaction, which was not evidently observed in the $^{48}$Ca-induced reactions in previous studies. The cross sections of the 3n and 4n channels of the $^{242}$Pu + $^{50}$Ti reaction of 0.32$^{+0.34}_{-0.18}$ pb and 0.22$^{+0.27}_{-0.15}$ pb, respectively, were measured at excitation energy of the $^{292}$Lv compound nucleus E$^{*}$ = 41 MeV. The cross section of the 4n-evaporation channel of the $^{238}$U + $^{54}$Cr reaction, leading to the same compound nucleus, at E$^{*}$ = 42 MeV of 36$^{+46}_{-24}$ fb turned out to be approximately 15 times lower than the total cross section of the $^{242}$Pu + $^{50}$Ti reaction at close excitation energy. Thus, for the first time, it was convincingly proved in an experiment that the reactions of isotopes of actinide elements with $^{50}$Ti are an order of magnitude preferable to reactions with $^{54}$Cr for the synthesis of new elements 119 and 120.
