For the experiment, the scientists shot at a 300-nanometer-thick foil of curium with accelerated calcium nuclei. In the collisions studied, the atomic nuclei of the two elements touched, and formed a compound system for an extremely short time. Before the compound system could break apart again, after about a sextillionth of a second, the two nuclei involved exchanged a number of their nuclear building-blocks. Different isotopes formed as the end products of this exchange.
The isotopes of berkelium, neptunium, and americium discovered in the GSI experiment were created as the end products of such collisions. They are unstable and decay after a few milliseconds or seconds, depending on the isotope. All of the resulting decay products can be separated and analyzed using special filters composed of electrical and magnetic fields. The scientists used all of the decay products detected to identify the new isotope that has been created.
“By using this method, we have succeeded in generating many different atomic nuclei at once,” says Sophia Heinz, the head of the experiment. “Our results are especially important for the study of super-heavy elements. New isotopes, in particular those of super-heavy elements, which contain an especially large number of neutrons, cannot be made by any other method. Experiments aimed at creating these neutron-rich nuclei are already being prepared.”
The current experiments will make it possible to explore previously unknown areas on the isotope chart. The elements 107 to 112 were discovered using the same experimental facility at GSI. The mechanisms responsible for the production of new isotopes will also be studied at the planned accelerator center FAIR in the future.
By the discovery of the four new isotopes, on the ranking list GSI moves closer to the laboratory which discovered the most isotopes. Head of the ranking list at the moment is the Lawrence Berkeley National Laboratory in the USA. GSI is on the second place.