A combination of physics and chemistry helped researchers identify the two “new” chemical elements – 113 and 115. The elemental discoveries took place at the Russian nuclear research centre (JNIR) in Dubna in 2003, but ongoing experiments are underway to provide additional evidence.
Heavy elements decay by emitting alpha particles (helium nucleus). American, Russian and Swiss scientists used this decay to prove the existence of elements 115 and its alpha decay product 113. In order to synthesize atoms of element 115 a rotating target disc of americium was bombarded with a calcium beam. Fusion between Americium and calcium produced a detectable quantity of 115 atoms.
However the formation of the atoms was not enough to prove the element’s existence as its atoms only exist for a tenth of a second and are difficult to detect. The radiochemical experiments proved much more successful yielding a provable five times as many atoms.
As expected, element 115 emits an alpha particle to decay to element 113. Four subsequent emissions produce dubnium, element 105. A copper plate was held behind the rotating americium disc to collect all element 115 atoms emitted from the target. The researchers then used liquid chromatography techniques to observe fifteen atoms of dubnium.
The decay pattern of these atoms supported the physics experiments, thus proving the earlier discovery of element 115 and its offspring element 113. All elements below atomic number 113 are already known.
Quite astonishingly a press release today from the Paul Scherrer Institute in Switzerland seemed to imply that these elemental discoveries were recent and that somehow they were down to the PSI. This is, not the case. Dozens of researchers were involved in the discovery, which was reported on Sciencebase and elsewhere in September 2003.
Take a look here for a timeline of elemental discoveries