Klaus Ruedenberg wins prestigious award

Klaus Ruedenberg
Klaus Ruedenberg

Klaus Ruedenberg continues to produce award-winning theoretical chemistry research at age 97.

Ruedenberg, Distinguished Professor Emeritus of chemistry, will receive the 2018 Schrödinger Medal from the World Association of Theoretical and Computational Chemists (WATOC).

"Klaus is a hero to almost everyone in the field," said Mark Gordon, Distinguished Professor of chemistry, and one of Ruedenberg's former postdoctoral students. "He is a true scientist and a true gentleman. As a colleague once said: He is one of the men, not one of the boys."

Ruedenberg's scientific work is focused on the understanding and prediction of molecular structure and spectra as well as chemical bonding and reactions, based on the quantum theory of electrons and nuclei.

"Certain problems have challenged me for a long time, and I feel that I am close to solving them, notably regarding the fundamental understanding of chemical bonding," Ruedenberg said. "Doing science keeps my mind fresh."

The Schrödinger Medal is named after Erwin Schrödinger, one of the creators of the field of quantum mechanics, which governs what happens at the atomic and molecular level. It is awarded each year to one outstanding theoretical and computational chemist. WATOC's citation states that Ruedenberg received the award "for advancing quantum chemistry through seminal innovations, pioneering the deduction of bonding concepts from rigorous wave mechanical analyses and, notably, identifying the fundamental physical origin of covalent bonding."

Every three years WATOC holds an international conference at which the most recent three medals are presented and the awardees present a lecture. Ruedenberg is scheduled to receive his medal at the 2020 meeting, in the week before his 100th birthday.

He was born in Germany but, being of Jewish background, left in 1938, amid discriminations by the Hitler regime, for Switzerland. Aiming at a practical profession, he studied chemistry in Fribourg but, because of his preference for the mathematical sciences, switched to theoretical physics in Zürich. In 1948 he followed his doctoral advisor, Gregor Wentzel, to the University of Chicago, a hub for physics at the time. Interestingly, about a decade earlier, at the University of Wisconsin, Wentzel had been the doctoral advisor of John V. Atanasoff, who subsequently created the digital computer at Iowa State University.

After finishing his doctoral work, Ruedenberg accepted a research associateship in theoretical chemistry with Robert S. Mulliken, later a Nobel Prize winner, at the University of Chicago. He hoped to be able to combine his background in both chemistry and theoretical physics.

At that time, in the early 1950s, theoretical chemistry was an emerging field and many scientists doubted that it had a future. But as the capabilities of electronic computers increased, the field gradually grew.

"I was fortunate that computers became more and more powerful, so that I did not have to regret my choosing this field, but became one of its pioneers," Ruedenberg said.

The Chemistry Department and the Ames Laboratory at Iowa State University were among the few places that foresaw the future importance of theoretical chemistry and, in 1955, asked Ruedenberg to join its faculty. In the subsequent decades, he developed a research program in fundamental theoretical chemistry with the strong support of the Ames Laboratory. He continued to work at Iowa State until his retirement in 1991, at which time Gordon returned to take over the helm of theoretical chemistry at Iowa State University.

"I have been fortunate that Mark came here. He has a large active research group with a substantial set of computers," Ruedenberg said. "His presence has stimulated and facilitated the continuation of my research. We also have collaborated on certain research projects."

Gordon was also a recipient of the Schrödinger Medal in 2014. In turn, Gordon was the doctoral adviser to Theresa Windus, who has since returned as a professor of chemistry to join the theoretical chemistry faculty at Iowa State University. Another former doctoral student of Ruedenberg's, Michael Schmidt, became a postdoctoral fellow with Gordon and returned with him to Iowa State as a senior research scientist.

"Thus, the foresight of the physical chemists at our department and the Ames Laboratory in the early 1950's has led to a strong and visible tradition in quantum-theoretical chemistry at Iowa State University," Ruedenberg said.

Ruedenberg's scientific legacy is highly regarded by his students as well as by the scientific community. He has received honorary doctorates from the Universities of Basel (Switzerland), Bielefeld (Germany) and Siegen (Germany). He has received the Midwest Award of the American Chemical Society as well as the National Award for Theoretical Chemistry of the American Chemical Society. He is a member of the International Academy of Quantum Molecular Sciences, an honorary member of the International Academy of Mathematical Chemistry, and an honorary director of the International Society for Theoretical Chemical Physics. He is a fellow of the American Association for the Advancement of Science, the American Physical Society and the American Institute of Chemists.

"Klaus is one of the few people in the world who has thought so deeply about the nature of the chemical bond," Windus said. "His current research is providing a very unique and theoretically sound approach to this fundamental issue in chemistry. In addition, Klaus has made seminal contributions in how we treat molecules with complex electronic configurations and highly accurate methods to compute energetic information."

He continues to be fascinated by the challenges of theoretical chemistry and shows no sign of stopping.

"I have always wanted to understand the origin of the many kinds of bonding between atoms in a way that is really faithful to the way the Schrödinger equation works," he said. "The thought of retiring is not appealing to me."