α decay of a new isotope,Ra204

Isotopes in the light actinide region with N<126, Z≳82 have been produced in the reaction of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ on ${}_{}{}^{182}{}_{}{}^{}\mathrm{W}$ at beam energies of 164 and 170 MeV. Evaporation residues were selected using an in-flight mass separator, the Argonne Fragment Mass Analyzer, and implanted in a double-sided silicon strip detector. The charge-to-mass ratio of implanted ions, and energies and half-lives of correlated α-decay events have been used to make isotopic identifications. The α decay from the ground state of ${}_{}{}^{204}{}_{}{}^{}\mathrm{Ra}$ has been observed with an α-particle energy of 7.488(12) MeV and a half-life of ${45}_{\mathrm{-}21}^{+55\mathrm{}}$ ms. Previous results concerning the decay of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Ra}$ were also confirmed.