Abstract
We presented the results of the series of experiments on the synthesis of Mc isotopes in the 243Am + 48Ca reaction performed at the new separator DGFRS-2 and cyclotron DC280 of the SHE Factory at FLNR JINR. There were registered 110 new 288Mc decay chains, 10 289Mc chains, and 4 287Mc chains. Alpha decay of 268Db with an energy of 7.6–8.0 MeV, half-life $$16_{{ - 4}}^{{ + 6}}$$ h and α-branch $$51_{{ - 12}}^{{ + 14}}$$ % was registered for the first time together with a new spontaneously fissioning isotope 264Lr with a half-life of $$4.8_{{ - 1.3}}^{{ + 2.2}}$$ h The measured cross section of the 243Am(48Ca, 3n)288Mc reaction was $$17.1_{{ - 4.7}}^{{ + 6.3}}$$ pb, which is the largest for known superheavy nuclei. A new isotope 286Mc was synthesized with a half-life of 20 $$_{{ - 9}}^{{ + 98}}$$ ms and an α-particle energy of 10.71 ± 0.02 MeV. Spontaneous fission of 279Rg was first observed in one of the four new decay chains of 287Mc. The reaction excitation function was measured at six 48Ca energies in the range of 239–259 MeV, which led to the first observation of the 5n channel with a cross section of 0.5 $$\begin{array}{*{20}{c}} { + 1.3} \\ { - 0.4} \end{array}$$ pb. The decay properties of 20 previously known isotopes have been determined with higher accuracy.