Credit for the synthesis of element 99 was given to the Berkeley team of Ghiorso et. al. in 1952 and the radioactive metal was named for Albert Einstein. The photo above shows about 0.3 micrograms of an unidentified Es compound. Evidence for the feasibility of the synthesis came from the debris of the first hydrogen bomb explosion in which U-238 was apparently transformed into U-253 which becomes Es-253 by the loss of seven beta particles.
The laboratory synthesis of Es-253 begins with Pu-239 and goes through a five step process. The longest-lived isotope is Es-254 with a half-life of 276 days.
Stephen R. Marsden (ChemTopics)