α decay of a new isotope ${}_{}{}^{209}{}_{}{}^{}\mathrm{Th}$

The new neutron deficient isotope ${}_{}{}^{209}{}_{}{}^{}\mathrm{Th}$ has been produced in the reaction of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ on ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ at beam energy of 171 MeV. Evaporation residues were separated in flight from beam by a JAERI recoil mass separator, and implanted in a position sensitive strip detector. The genetic correlation of α-decay events, their energies and half-lives has been used to identify isotopes. An α-decay energy and a half-life of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Th}$ have been determined to be 8.080(50) MeV and 3.$8_{\mathrm{-}1.5}^{+6.9\mathrm{}}$ ms, respectively. © 1996 The American Physical Society.