Karl-Ludwig Kratz
Karl-Ludwig Kratz (born April 23, 1941 in Jena ) is a German nuclear chemist and astrophysicist . He is Professor of Nuclear Chemistry at Johannes Gutenberg University in Mainz and Adjunct Professor of Physics at the University of Notre Dame in South Bend , Indiana .
Nuclear chemistry
He is the eldest son of the chemist Ludwig Kratz , who was part of the 41 glassmakers from the Schott company in Jena who were brought to West Germany by the US armed forces in 1945. Accordingly, he spent his school days in Landshut and then in Mainz. He studied chemistry at the Johannes Gutenberg University in Mainz. At the Institute for Nuclear Chemistry founded by Fritz Straßmann , he received his doctorate in 1972 under the guidance of Günter Herrmann with the thesis Decay properties of short-lived neutron-rich halogen isotopes and their yields in the fission of uranium-235 with thermal neutrons . For this purpose, fast and at the same time highly selective radiochemical separation processes for very short-lived, neutron-rich nuclei from the fission of uranium-235 with thermal neutrons from the TRIGA MARK / II research neutron source of the institute were developed. The problem of the secretion of often only small amounts of the nuclide to be examined from the fission product mixture was to occupy Kratz throughout his research life. With these separation methods, the decay properties of neutron-rich nuclides such as half-life and the emission probability for β-delayed neutrons (a type of decay that generally only occurs in nuclei with a high neutron excess ) were determined.
Karl-Ludwig Kratz developed methods to measure the energy of these delayed neutrons. Together with the spectroscopy of the characteristic gamma radiation emitted at the same time , the core structure of short-lived fission products could be determined. These neutron-rich nuclei data can be found e.g. B. Application in reactor technology (in particular, the data on delayed neutrons are important for controlling the reactors) and nucleosynthesis (see below).
With the knowledge of the gamma radiation characteristic of each nuclide, the contents of (trace) elements in samples can be determined with the instrumental neutron activation analysis, a procedure that Karl-Ludwig Kratz and his working group use in environmental analysis and geochemistry .
Today, experiments on the core structure are mainly carried out by international collaborations at mostly transnational research institutions. For a long time, Kratz and his working group have been working on research reactors and accelerators such as the high-flux reactor of the Laue-Langevin Institute in Grenoble , the ISOLDE separator at the European nuclear research center CERN near Geneva , the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, the National Superconducting Cyclotron Laboratory NSCL at the Michigan State University in East Lansing, Michigan , and other more nationally operated institutions.
Nuclear astrophysics
The experimental data of short-lived, neutron-rich nuclides are incorporated into nuclear astrophysics by Kratz . His field is nucleosynthesis , the construction of the elements from the ashes of the Big Bang into stars. Short-lived, extremely neutron-rich nuclei occur in the so-called r-process (r = rapid), in which during a star explosion ( type II supernova ) short-term high neutron fluxes cause medium-weight nuclei in the iron group to alternate between neutron capture - and β-decay processes heavy elements are synthesized up to thorium and uranium . Frequency maxima in the distribution of the elements in the solar system, which were determined cosmochemically from primitive meteorites ( carbonaceous chondrites ), can be explained with the influence of the core structure, especially magic neutron numbers.
The work of Karl-Ludwig Kratz (in close collaboration with Friedrich-Karl Thielemann , University of Basel ) indicated that the core structure of nuclei with a high neutron excess differs from that of nuclei near the valley of β-stability, which are accessible for investigation in earthly laboratories , deviates. The comparison of the calculated abundances of the elements with astronomical observations of old stars with extremely low metallicity in the halo of the Milky Way (such as CS22892-052 , CS31082-001 or BD + 17 ° 3248 ) makes it possible to determine the age of these stars, which is already a few hundred Formed millions of years after the Big Bang . ecfix
leisure
In his spare time, Kratz enjoys sailing in summer and alpine skier in winter. He has often succeeded in combining work and recreational sport. Mention should be made of the sailing regattas at the conferences on the Masurian Lakes and the optimal combination of fully automated data acquisition in experiments at the Laue-Langevin Institute , Grenoble , with downhill runs in the nearby winter sports areas such as Chamrousse.
In March 2003 he started a series of workshops on Nuclear Astrophysics in the Salzburg community of Rußbach am Pass Gschütt . As part of the Virtual Institute of Nuclear Structure and Nuclear Astrophysics - VISTARS , established by the Helmholtz Association of German Large Research Institutions , these meetings are intended to bring together students and experienced researchers and university teachers to establish contact, in the lecture hall and on the ski slope.
Honors
In 1999 the American Chemical Society awarded him (as only a few non-Americans) the Glenn T. Seaborg Award for Nuclear Chemistry , which his doctoral supervisor Günter Herrmann had received in 1988. In 2004 the GSI Exotic Nuclei Community presented him with their GENCO Award . On the occasion of his 65th birthday, his employees asked him to sponsor the star BD + 17 ° 3248 as Karl-Ludwig Kratz's star . In 2014 he was awarded the Hans A. Bethe Prize by the American Physical Society .
Fonts
- Karl-Ludwig Kratz: Decay properties of short-lived neutron-rich halogen isotopes and their yields in the fission of uranium-235 with thermal neutrons . Univ. Mainz, 1972 (dissertation).
Web links
- Nuclear Chemistry Award ( Memento from March 11, 2007 in the Internet Archive ) on chemie.uni-mainz.de
- List of publications ( memento of March 11, 2007 in the Internet Archive ) on chemie.uni-mainz.de
- Helmholz on helmholtz.de
- vistars.de
- Hans A. Bethe Prize
Individual evidence
- ↑ Life data, publications and academic family tree of Karl-Ludwig Kratz at academictree.org, accessed on February 24, 2018.
| personal data | |
|---|---|
| SURNAME | Kratz, Karl-Ludwig |
| BRIEF DESCRIPTION | German nuclear chemist and astrophysicist |
| DATE OF BIRTH | April 23, 1941 |
| PLACE OF BIRTH | Jena |