Synthesis and decay properties of isotopes of element 110: Ds273 and Ds275

The ²³²Th(⁴⁸Ca,5n)²⁷⁵Ds and ²³⁸U(⁴⁰Ar,5n)²⁷³Ds 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 ²⁷⁵Ds with a half-life of 0.43_-0.12+0.29 ms and {α}-particle energy of 11.20±0.02 MeV was synthesized in the ⁴⁸Ca-induced reaction with the actinide nucleus and identified by measuring correlated {α} decays ending in known nuclei. The decay properties of nuclei originating from ²⁷³Ds and ²⁷⁵Ds are compared with theoretical calculations and decay schemes are proposed. The cross sections of the ²³²Th(⁴⁸Ca,5n)²⁷⁵Ds reaction of 0.11_-0.09+0.46 and 0.34_-0.16+0.59 pb were measured at excitation energies of the ²⁸⁰Ds compound nucleus E*=51 and 56 MeV, respectively. The cross section of the $5n$-evaporation channel of the ²³⁸U+⁴⁰Ar reaction at E*=49 MeV of 0.18_-0.12+0.44 pb turned out to be comparable to that for ²⁷⁵Ds at close excitation energy.