How do you find a new element, like the recently discovered superheavy chemical element 115?
Elements beyond atomic number 104 are referred to as superheavy elements and are produced at accelerator laboratories and generally decay after a short time. Initial reports about an element with atomic number 115 were released from a research center in Russia in 2004 but their indirect evidence was insufficient for an official discovery.
The latest group was able to present a way to directly identify new superheavy elements by taking a sample of the exotic element americium and depositing a layer on a thin foil, which was subsequently bombarded with calcium ions at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt. For the first time, the exploitation of a new detector system allowed registering photons along with the alpha-decay of the new element and its daughter products.
Measured photon energies correspond to those expected for X-rays from these products and thus serve as the element's fingerprint.
"This can be regarded as one of the most important experiments in the field in recent years, because at last it is clear that even the heaviest elements' fingerprints can be taken," said Professor Dirk Rudolph from Lund University in Sweden and Professor Christoph Düllmann, professor at Mainz University and leading scientist at GSI Darmstadt. "The result gives high confidence to previous reports. It also lays the basis for future measurements of this kind."
Element 115 is yet to be named: a committee comprising members of the international unions of pure and applied physics and chemistry will review the new findings and decide whether further experiments are needed to acknowledge official discovery of the element. Only after acceptance can a name may be proposed by the discoverers.
Besides the X-ray events, the researchers have also obtained data giving them a deeper insight into the structure and properties of the heaviest currently known atomic nuclei. This paves the way towards improved predictions for properties of nuclei beyond the border of current knowledge.
Upcoming in the scientific journal The Physical Review Letters.