Alpha decay of Fr 215

The $\ensuremath{\alpha}$-decay property of $^{215}\mathrm{Fr}$ has been studied by the pulsed-beam method, in which $^{215}\mathrm{Fr}$ was produced in the $^{209}\mathrm{Bi}(^{12}\mathrm{C},\ensuremath{\alpha}2n)$ reaction and its $\ensuremath{\alpha}$ decay was measured between natural beam bursts of the cyclotron. The ground state of $^{215}\mathrm{Fr}$ was found to decay with ${E}_{\ensuremath{\alpha}}=9.355\ifmmode\pm\else\textpm\fi{}0.010$ MeV and ${t}_{\frac{1}{2}}=0.12\ifmmode\pm\else\textpm\fi{}0.02$ \ensuremath{\mu}sec. The reduced $\ensuremath{\alpha}$ width of $^{215}\mathrm{Fr}$ is shown to fit the systematical trend of $N=128$ isotones very well and to agree with the simple shell-model calculation. Distributions of recoil angles for reaction products in the ($^{12}\mathrm{C},\ensuremath{\alpha}\mathrm{xn}$) reaction were found to be quite different from those for ($^{12}\mathrm{C},xn$) products, giving a convenient method of distinguishing these reaction products.