ALPHA-DECAY OF A NEW ISOTOPE, RA-204

Isotopes in the light actinide region with N<126, Z82 have been produced in the reaction of Si28 on W182 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 Ra204 has been observed with an α-particle energy of 7.488(12) MeV and a half-life of 45-21+55 ms. Previous results concerning the decay of Ra205 were also confirmed. © 1995 The American Physical Society.