Production and decay of the isotopes of Hs were studied in the ${}^{226}$Ra+${}^{48}$Ca reaction at beam energies $E_{\mathrm{lab}}=229$, 234, and 241 MeV. At the $E_{\mathrm{lab}}=234$ MeV energy, the maximum of the 4$n$-evaporation channel of the reaction, six identical $\alpha$-SF decay chains of the nucleus ${}^{270}$Hs were detected corresponding to a cross section of ${\sigma }_{4n}={16}_{-7}^{+13}$ pb. At the other ${}^{48}$Ca energies, no Hs isotopes were observed. Nuclei of ${}^{270}$Hs undergo $\alpha$ decay with a $Q_{\alpha }=9.15\pm 0.08$ MeV and the half-life of the daughter spontaneous fission (SF) isotope ${}^{266}$Sg is 0.28${}_{-0.08}^{+0.19}$ s, in good agreement with the data previously observed in the ${}^{248}$Cm(${}^{26}$Mg,4$n$)${}^{270}$Hs reaction. The partial $\alpha$-decay half-life of ${}^{270}$Hs was measured for the first time: $T_{\alpha }=7.6_{-2.2}^{+4.9}$ s. For the spontaneous fission, we determined a lower limit $T_{\mathrm{SF}}⩾10$ s. Decay properties of ${}^{270}$Hs corroborate theoretical predictions of its relatively high stability caused by the effect of the deformed shells at $Z=108$ and $N=162$.

• Received 28 September 2012

DOI:https://doi.org/10.1103/PhysRevC.87.034605