Nobelium


The discovery of nobelium, element 102, is still an unresolved question, since its discovery had been announced by three different research groups. The same technique was employed by all groups working on element 102. The recoil procedure involves irradiating a thin target with heavy ions and then catching the recoil atoms on a foil. This method has several advantages such as the possibility of immediate separation of the short-lived recoil atoms from the intense radioactivity of the target, the ability to do repeated irradiations with the same target and the possibility of adapting the technique to identify the original recoil atoms by collecting recoils from the alpha decay of the initial product atoms.

The first group, consisting of scientist from Argonne National Laboratory, USA, Harwell Atomic Energy Research Establishment, England and the Nobel Institute of Physics, Sweden, reported the isolation of element 102 in 1957. This group included P. R. Fields, A. M. Friedman, J. Milstred, H. Atterling, W. Forsling, L. W. Holm and B. Astrom. They irradiated a target of Cm 244, Cm 246 and Cm 248 with C 13 ions, obtaining an isotope with mass number between 251 and 255, but with atomic number considered to be 102. This group proposed the name Nobelium in honor to Alfred Nobel.

Approximately one year later, another group of scientists working at the Lawrence Radiations Laboratory, University of California, succeeded in the irradiation of a similar target with C 12 ions. They detected the isotope 254 with a half-life of 3 seconds. This group identified the isotope 255 prepared through the irradiation of Cf 252 with boron ions. The group was composed by the scientists A. Ghiorso, T. Sikkeland, J. R. Walton and S. G. Seaborg.

The third group of scientists working in 1957 at the Dubna Institute in the former USSR, also reported the production of isotopes of element 102. Their attempts involving irradiating Pu 239 and Pu 241 with O 16 ions were not very successful. Only in 1963 they were able to report the detection of No 256 through the irradiation of U 238 with Ne 22 ions and using a method similar to the other research groups.