Synthesis and decay properties of isotopes of element 110: ${}_{273}\mathrm{Ds}$ and ${}_{275}\mathrm{Ds}$

The ${}_{232}\mathrm{Th}$(${}_{48}\mathrm{Ca},5n$)${}_{275}\mathrm{Ds}$ and ${}_{238}U$(${}_{40}\mathrm{Ar},5n$)${}_{273}\mathrm{Ds}$ reactions have been studied at the gas-filled separator DGFRS-2 at the Superheavy Element Factory at Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. For the first time, a new isotope ${}_{275}\mathrm{Ds}$ with a half-life of $0.{43}_{-0.12}^{+0.29}$ ms and α-particle energy of $11.20\pm 0.02$ MeV was synthesized in the ${}_{48}\mathrm{Ca}$-induced reaction with the actinide nucleus and identified by measuring correlated α decays ending in known nuclei. The decay properties of nuclei originating from ${}_{273}\mathrm{Ds}$ and ${}_{275}\mathrm{Ds}$ are compared with theoretical calculations and decay schemes are proposed. The cross sections of the ${}_{232}\mathrm{Th}$(${}_{48}\mathrm{Ca},5n$)${}_{275}\mathrm{Ds}$ reaction of $0.{11}_{-0.09}^{+0.46}$ and $0.{34}_{-0.16}^{+0.59}$ pb were measured at excitation energies of the ${}_{280}\mathrm{Ds}$ compound nucleus $E^{*}=51$ and 56 MeV, respectively. The cross section of the $5n$-evaporation channel of the ${}_{238}U+{}_{40}\mathrm{Ar}$ reaction at $E^{*}=49$ MeV of $0.{18}_{-0.12}^{+0.44}$ pb turned out to be comparable to that for ${}_{275}\mathrm{Ds}$ at close excitation energy.