Karl-Ludwig Kratz
Karl-Ludwig Kratz (1941–2025) was a German nuclear chemist and astrophysicist. He was a professor of nuclear chemistry at Johannes Gutenberg University of Mainz and an adjunct professor of physics at the University of Notre Dame. His main work focused on very neutron-rich atomic nuclei and beta-delayed neutron emission (neutrons released after beta decay). These exotic isotopes are produced in reactions like fission or proton-induced spallation of heavy elements such as uranium, and Kratz developed highly selective chemical and physical methods to separate them from many other short-lived products. He worked with international teams at facilities such as the ILL in France, CERN in Switzerland, and the National Superconducting Cyclotron Laboratory in Michigan.
Kratz linked nuclear data to how elements form in stars, especially during the rapid neutron capture process (r-process). With Friedrich-Karl Thielemann, he modeled element production in supernovae and compared the results with observations in old stars. Studies of ultra-metal-poor Population II stars in the galactic halo showed patterns that resemble the solar r-process pattern, helping scientists estimate the ages of these stars—about 13 billion years in some cases.
He received major awards for his work, including the Nuclear Chemistry Award (now the Glenn T. Seaborg Award) from the American Chemical Society in 1999 and the Hans Bethe Prize from the American Physical Society in 2014. Kratz passed away on March 23, 2025, at age 83.
This page was last edited on 2 February 2026, at 09:05 (CET).