New world record at GSI – Hans Geissel has produced the largest number of nuclides

He overtook his colleague Professor Gottfried Münzenberg in the world rankings with the production of 59 new nuclides. Münzenberg, who also conducted research at GSI before his retirement in 2005, previously held the world record with 219 nuclides discovered. The Lawrence Berkeley National Laboratory in Berkeley, California (USA) is the leading laboratory in the statistics, with 635 discovered nuclides. GSI is ranked second with 435.

The new rankings were made public by Professor Michael Thoennessen, a researcher at Michigan State University, during a visit to GSI in February 2013.

“None of this would have been possible without my colleagues and the outstanding research opportunities offered at GSI,” Geissel says. “I’m especially grateful to our former Director, Professor Paul Kienle, who recently passed away. Professor Kienle was the one who made it possible to construct the fragment separator FRS and establish the associated research program. Until just a short time ago, he also played an active role in many experiments, especially those involving the coupling with the storage ring.” Geissel is a professor at Justus Liebig University Giessen. He also directs the research conducted with the GSI fragment separator, which was used to measure most of the newly discovered nuclides. In addition, Geissel is playing a major role in the planning process for the super fragment separator to be installed at the new accelerator facility FAIR. “The Super-FRS at FAIR will enable us to produce many new nuclides and measure their properties in a very short time,” says Geissel. “We are confident that we can improve on the world record with FAIR. We strive hard to complete the facility and make it available for our international research community.”

“The decisive factor in the discovery of a new nuclide is the publication of the measured mass and charge,” says Michael Thoennessen, whose “Discovery of Isotopes Project” compiles statistics on the history of nuclide discoveries. “When a scientist has experimentally determined these two values, we consider the discovery to have been proved, and we then add his or her name to the list.” Working together with his students, Thoennessen has summarized the discoverers of all nuclides by person and by laboratory on the basis of scientific publications. Professor Marek Pfützner of the University of Warzsaw, who is also heavily involved in GSI experiments, occupies second place on the list of persons. Gottfried Münzenberg, who was a professor at Johannes Gutenberg University Mainz and a researcher at GSI, is now third. The list of the top 25 nuclide discoverers includes 22 who have carried out research at GSI. The latest results of Geissel and his colleagues were published in 2012 in the scientific journal Physics Letters B.

“Hans Geissel is an outstanding pioneer in the hunt for new nuclides produced in stellar explosions in our cosmos. He has greatly increased our understanding of 'life and death' of stars with his measurements conducted at GSI”, says Professor Karlheinz Langanke, director of research at GSI and theoretical physicist at the University of Darmstadt.

All of the matter of our earth is made of atoms. All atoms with the same electric charge in their nuclei are classified as being nuclei of the same chemical element. To date, we know of 114 such chemical elements. Each element comes in different types known as isotopes, whose atomic nuclei have the same electrical charge but different masses. The discovery of a new nuclide is thus also the discovery of a new isotope. Researchers have observed more than 3,000 different isotopes, and another thousand as yet unknown ones are forecast to exist.

Scientists are particularly interested in very heavy isotopes of an element. Such isotopes play a major role in our understanding of how the elements are created in stars and in stellar explosions. However, due to their short lifetimes, they do not occur naturally on earth. That's why scientists attempt to create them artificially in the laboratory. They do this by accelerating atomic nuclei and colliding them with different materials. New isotopes occur as fragments from the collisions. The fragments can then be sorted and studied using the fragment separator at GSI.