Several new alpha-emitting isotopes of francium have been produced by the reactions ${\mathrm{Au}}^{197}({\mathrm{O}}^{16}, xn){\mathrm{Fr}}^{213-x}$, ${\mathrm{Tl}}^{203}({\mathrm{C}}^{12}, xn){\mathrm{Fr}}^{215-x}$, ${\mathrm{Tl}}^{205}({\mathrm{C}}^{12}, xn){\mathrm{Fr}}^{217-x}$, and ${\mathrm{Pb}}^{208}({\mathrm{B}}^{11}, xn){\mathrm{Fr}}^{219-x}$. The nuclides studies lie on or below the 126-neutron closed shell. Their alpha-decay properties are as follows:

Alpha-decay reduced widths ${\delta }^2$ 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.

• Received 20 September 1963

DOI:https://doi.org/10.1103/PhysRev.133.B1373