Alpha-Decay Properties of Some Francium Isotopes Near the 126-Neutron Closed Shell

Abstract

Several new alpha-emitting isotopes of francium have been produced by the reactions ${\mathrm{Au}}^{197}({\mathrm{O}}^{16}, xn){\mathrm{Fr}}^{213\ensuremath{-}x}$, ${\mathrm{Tl}}^{203}({\mathrm{C}}^{12}, xn){\mathrm{Fr}}^{215\ensuremath{-}x}$, ${\mathrm{Tl}}^{205}({\mathrm{C}}^{12}, xn){\mathrm{Fr}}^{217\ensuremath{-}x}$, and ${\mathrm{Pb}}^{208}({\mathrm{B}}^{11}, xn){\mathrm{Fr}}^{219\ensuremath{-}x}$. The nuclides studies lie on or below the 126-neutron closed shell. Their alpha-decay properties are as follows: Alpha-decay reduced widths ${\ensuremath{\delta}}^{2}$ were calculated by using beta-decay systematics from this region to estimate the beta branching ratios. These reduced widths are compared to those of the isotonic polonium isotopes.