Production ofDb262in theCm248(F19,5n)Db262reaction and decay properties ofDb262andLr258

Abstract

The nuclide $^{262}\mathrm{Db}$ was produced in the $^{248}\mathrm{Cm}$($^{19}\mathrm{F}$,5$n$)$^{262}\mathrm{Db}$ reaction at beam energies of 103.1 and 97.4 MeV. Decay properties of $^{262}\mathrm{Db}$ were investigated with a rotating wheel apparatus for \ensuremath{\alpha} and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated \ensuremath{\alpha}-\ensuremath{\alpha} and \ensuremath{\alpha}-SF decay chains, a total of 76 chains were assigned to $^{262}\mathrm{Db}$ and its \ensuremath{\alpha}-decay daughter nuclide $^{258}\mathrm{Lr}$. No correlated decay chain was observed for Db produced in the $^{248}\mathrm{Cm}$($^{19}\mathrm{F}$,4$n$)Db reaction and its daughter Lr. The half-lives of $^{262}\mathrm{Db}$ and $^{258}\mathrm{Lr}$ were measured to be ${T}_{1/\phantom{\rule{0.0pt}{0ex}}2}=33.{8}_{\ensuremath{-}3.5}^{+4.4}$ and $3.{54}_{\ensuremath{-}0.36}^{+0.46}\mathrm{s}$, respectively, and they confirmed the literature data. The \ensuremath{\alpha}-particle energy $({E}_{\ensuremath{\alpha}})$ and intensity (${I}_{\ensuremath{\alpha}}$) of $^{262}\mathrm{Db}$ were revised to ${E}_{\ensuremath{\alpha}}$ = 8.46 \ifmmode\pm\else\textpm\fi{} 0.04 MeV (${I}_{\ensuremath{\alpha}}$ = 70 \ifmmode\pm\else\textpm\fi{} 5%) and ${E}_{\ensuremath{\alpha}}$ = 8.68 \ifmmode\pm\else\textpm\fi{} 0.03 MeV (${I}_{\ensuremath{\alpha}}$ = 30 \ifmmode\pm\else\textpm\fi{} 5%). The SF activity with ${T}_{1/2}$ = 30.2 \ifmmode\pm\else\textpm\fi{} 6.1 s was assigned to $^{262}\mathrm{Db}$, and the SF branch of $^{262}\mathrm{Db}$ was determined to be ${b}_{\mathrm{SF}}$ = 52 \ifmmode\pm\else\textpm\fi{} 4%. From an observation of two SF decays which correlated to the \ensuremath{\alpha} decay of $^{262}\mathrm{Db}$, an electron capture (EC) decay with ${b}_{\mathrm{EC}}$ = 2.6 \ifmmode\pm\else\textpm\fi{} 1.8% was suggested in $^{258}\mathrm{Lr}$. The production cross sections for the $^{248}\mathrm{Cm}$($^{19}\mathrm{F}$,5$n$)$^{262}\mathrm{Db}$ reaction were determined to be 2.1 \ifmmode\pm\else\textpm\fi{} 0.7 nb at 103.1 MeV and $0.{23}_{\ensuremath{-}0.11}^{+0.18}\mathrm{nb}$ at 97.4 MeV, whereas, those for the $^{248}\mathrm{Cm}$($^{19}\mathrm{F}$,4$n$)Db reaction were the upper limits of \ensuremath{\le}0.064 nb at 103.1 MeV and \ensuremath{\le}0.13 nb at 97.4 MeV. These cross sections are discussed by comparing with the literature data as well as the theoretical prediction.