Synthesis of rutherfordium isotopes in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">U</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>238</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Mg</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>26</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="italic">xn</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:msup><mml:mi/><mml:mrow><mml:mn>264</mml:mn><mml:mtext>−</mml:mtext><mml:mi>x</mml:mi></mml:mrow></mml:msup><mml:mi mathvariant="normal">Rf</mml:mi></mml:mrow></mml:math>reaction and study of their decay properties

Isotopes of rutherfordium ($^{258\ensuremath{-}261}\mathrm{Rf}$) were produced in irradiations of $^{238}\mathrm{U}$ targets with $^{26}\mathrm{Mg}$ beams. Excitation functions were measured for the $4n,5n$, and $6n$ exit channels. Production of $^{261}\mathrm{Rf}$ in the $3n$ exit channel with a cross section of ${28}_{\ensuremath{-}26}^{+92}$ pb was observed. $\ensuremath{\alpha}$-decay of $^{258}\mathrm{Rf}$ was observed for the first time with an $\ensuremath{\alpha}$-particle energy of 9.05 \ifmmode\pm\else\textpm\fi{} 0.03 MeV and an $\ensuremath{\alpha}/$total-decay branching ratio of 0.31 \ifmmode\pm\else\textpm\fi{} 0.11. In $^{259}\mathrm{Rf}$, the electron capture/total-decay branching ratio was measured to be $0.15\ifmmode\pm\else\textpm\fi{}0.04$. The measured half-lives for $^{258}\mathrm{Rf}$, $^{259}\mathrm{Rf}$, and $^{260}\mathrm{Rf}$ were $14.{7}_{\ensuremath{-}1.0}^{+1.2}$ ms, $2.{5}_{\ensuremath{-}0.3}^{+0.4}$ s, and $22.{2}_{\ensuremath{-}2.4}^{+3.0}$ ms, respectively, in agreement with literature data. The systematics of the $\ensuremath{\alpha}$-decay $Q$-values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the $N=152,Z=100$ deformed shell. The influence of the $N=152$ shell on the $\ensuremath{\alpha}$-decay $Q$-values for rutherfordium was observed to be similar to that of the lighter elements ($96\ensuremath{\leqslant}Z\ensuremath{\leqslant}102$). However, the $N=152$ shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements ($96\ensuremath{\leqslant}Z\ensuremath{\leqslant}102$).

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