Karl-Ludwig Kratz (born April 23, 1941, in

Jena Jena () is a German city and the second largest city in Thuringia. Together with the nearby cities of Erfurt and Weimar, it forms the central metropolitan area of Thuringia with approximately 500,000 inhabitants, while the city itself has a popu ...

Thuringia Thuringia (; german: Thüringen ), officially the Free State of Thuringia ( ), is a state of central Germany, covering , the sixth smallest of the sixteen German states. It has a population of about 2.1 million. Erfurt is the capital and larg ...

) is a German nuclear chemist and astrophysicist. He is professor for nuclear chemistry at the

Johannes Gutenberg University of Mainz The Johannes Gutenberg University Mainz (german: Johannes Gutenberg-Universität Mainz) is a public research university in Mainz, Rhineland Palatinate, Germany, named after the printer Johannes Gutenberg since 1946. With approximately 32,000 stu ...

and adjunct professor of physics at the

University of Notre Dame The University of Notre Dame du Lac, known simply as Notre Dame ( ) or ND, is a private Catholic research university in Notre Dame, Indiana, outside the city of South Bend. French priest Edward Sorin founded the school in 1842. The main campu ...

South Bend, Indiana South Bend is a city in and the county seat of St. Joseph County, Indiana, St. Joseph County, Indiana, on the St. Joseph River (Lake Michigan), St. Joseph River near its southernmost bend, from which it derives its name. As of the 2020 United S ...

. One of the main interests of Kratz is the study of nuclear structure of very neutron-rich isotopes. He concentrated on the beta-delayed neutron decay mode, especially the spectroscopy of the emitted neutrons. These isotopes are obtained by

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...

or proton induced

spallation Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary p ...

of heavy elements as uranium. In general, the extremely neutron-rich species of interest are produced together with an overwhelming amount of shorter-lived ones. Therefore, he is developing chemical and physical separation techniques with very high chemical selectivity. These studies are performed in international collaborations at high-flux reactors (

Institut Laue-Langevin An institute is an organisational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body. In some countries, institutes can ...

, France) or accelerator facilities as the

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...

in Switzerland or the

National Superconducting Cyclotron Laboratory The National Superconducting Cyclotron Laboratory (NSCL), located on the campus of Michigan State University was a isotope, rare isotope research facility in the United States.Bruns, Adam (January 2009How Are You Helping Companies Grow?''Site Sel ...

Michigan State University Michigan State University (Michigan State, MSU) is a public university, public Land-grant university, land-grant research university in East Lansing, Michigan. It was founded in 1855 as the Agricultural College of the State of Michigan, the fi ...

. The nuclear structure data are also applied by Kratz to

nucleosynthesis Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...

, especially the astrophysical

r-process In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", ...

. Elemental abundances from

Supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

explosions are calculated in close collaboration with

Friedrich-Karl Thielemann Friedrich-Karl "Friedel“ Thielemann (born 17 April 1951 in Mülheim an der Ruhr) is a German-Swiss theoretical astrophysicist. Thielemann studied at the TH Darmstadt, where he in 1976 he acquired his Diplom. In 1980 he earned his PhD under Wo ...

of the

University of Basel The University of Basel (Latin: ''Universitas Basiliensis'', German: ''Universität Basel'') is a university in Basel, Switzerland. Founded on 4 April 1460, it is Switzerland's oldest university and among the world's oldest surviving universit ...

. The calculated abundances are then compared to observed stellar abundances. Ultra-

metal-poor In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

Population II During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed th ...

stars in the Galactic Halo exhibit a scaled-down Solar System r-process abundance pattern. Comparing calculated and observed abundances for elements as the stable

europium Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...

with radioactive ones (

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...

and

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

) the age of these stars can be determined to about 13 billion years (see

Sneden's Star BPS CS22892-0052 (Sneden's Star) is an old population II star located at a distance of 4.7 kpc in the galactic halo. It belongs to a class of ultra- metal-poor stars ( Metallicity e/H-3.1), specifically the very rare subclass of neut ...

Cayrel's Star BPS CS31082-0001, named Cayrel's Star , is an old Population II star located in a distance of 2.1 kpc in the galactic halo. It belongs to the class of ultra-metal-poor stars (metallicity Fe/Hydrogen.html"_;"title="Iron.html"_;"title="/ ...

BD +17° 3248 BD, Bd or bd may refer to: In arts and entertainment * B. D. (Doonesbury), a major character in the ''Doonesbury'' comic strip * ''Bande dessinée'' (or "bédé"), a French term for comics * Bass drum, in sheet music notation * Brahe Djäkn ...

HE 1523-0901 HE 1523-0901 is the designation given to a red giant star in the Milky Way galaxy approximately 7500 light years from Earth. It is thought to be a second generation, Population II, or metal-poor, star ( e/Hnbsp;= −2.95). The star ...

). In 1999 he received the Nuclear Chemistry Award (now Glenn T. Seaborg Award) of the

American Chemical Society The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all d ...

. In 2014, the

American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...

rewarded him the Hans A. Bethe Prize.

References

{{DEFAULTSORT:Kratz, Karl-Ludwig 1941 births Living people 20th-century German chemists Academic staff of Johannes Gutenberg University Mainz University of Notre Dame faculty 21st-century German chemists Scientists from Jena