Isotopes of Einsteinium and Fermium Produced by Neutron Irradiation of Plutonium

Samples of einsteinium and fermium have been separated from neutron-irradiated plutonium and carefully purified. Four isotopes of einsteinium were found: 20.03-day E²⁵³, emitting 6.636-Mev and 6.24-Mev alpha particles and 42- and 393-kev gamma rays, both magnetic dipole transitions, and with a spontaneous fission half-life of 7×{}10⁵ years; 38.5-hr E²⁵⁴ᵐ, a beta emitter with 1.04-Mev beta rays and 0.680-Mev gamma rays; {~}320-day E²⁵⁴, an alpha emitter with 6.42-Mev alpha particles; and 24-day E²⁵⁵, a beta emitter. Two fermium isotopes were found: 3.24-hr Fm²⁵⁴ emitting 7.20-Mev alpha particles and with a spontaneous fission half-life of 246 days; and 21.5-hr Fm²⁵⁵ emitting 7.08-Mev alpha particles.