Rutherfordium

History

In 1964, workers at the Joint Nuclear Research Institute at Dubna (U.S.S.R.) bombarded plutonium with accelerated 113 to 115 MeV neon ions. By measuring fission tracks in a special glass with a microscope, they detected an isotope that decays by spontaneous fission. They suggested that this isotope, which had a half-life of 0.3 +/- 0.1 s might be 260-104, produced by the following reaction: ²⁴²Pu + ²²Ne --> ²⁶⁰Rf +4n.

Element 104, the first transactinide element, is expected to have chemical properties similar to those of hafnium. It would, for example, form a relatively volatile compound with chlorine (a tetrachloride).

The Soviet scientists have performed experiments aimed at chemical identification, and have attempted to show that the 0.3-s activity is more volatile than that of the relatively nonvolatile actinide trichlorides. This experiment does not fulfill the test of chemically separating the new element from all others, but it provides important evidence for evaluation. Data issued by Soviet scientists reduced the half-life of the isotope they worked with from 0.3 to 0.15 s.

Isotopes

In 1969 Ghiorso, Nurmia, Harris, K.A.Y. Eskola, and P.L. Eskola of the University of California at Berkeley reported that they had positively identified two, and possibly three isotopes of Element 104. The group indicated that, after repeated attempts, they produced isotope ²⁶⁰Rf reported by the Dubna groups in 1964.

The discoveries at Berkeley were made by bombarding a target of ²⁴⁹Cf with ¹²C nuclei of 71 MeV, and ¹³C nuclei of 69 MeV. The combination of ¹²C with ²⁴⁹Cf followed by instant emission of four neutrons produced Element ²⁵⁷Rf. This isotope has a half-life of 4 to 5 s, decaying by emitting an alpha particle into ²⁵³No, with a half-life of 105 s.

The same reaction, except with the emission of three neutrons, was thought to have produced ²⁵⁸Rf with a half-life of about 1/100 s.

Element ²⁵⁹Rf is formed by the merging of a ¹³C nuclei with ²⁴⁹Cf, followed by emission of three neutrons. This isotope has a half-life of 3 to 4 s, and decays by emitting an alpha particle into ²⁵⁵No, which has a half-life of 185 s.

Thousands of atoms of ²⁵⁷Rf and ²⁵⁹Rf have been detected. The Berkeley group believes their identification of ²⁵⁸Rf is correct, but attaches less confidence to this work than to their work on ²⁵⁷Rf and ²⁵⁹Rf.