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K-State Today

December 20, 2011



A high recognition: American Physical Society elects Thumm, Law as fellows for contributions to physics

By Communications and Marketing

Two Kansas State University physicists known for their work in theoretical atomic and liquid surface physics have been named fellows of the American Physical Society.

The society's council elected Uwe Thumm and Bruce Law, both professors of physics, for fellow status, which recognizes outstanding contributions to physics. The honor is limited to no more than one-half of 1 percent of the society's membership. The American Physical Society represents 48,000 members, including physicists in academia, national laboratories and industry in the United States and throughout the world.

Eight faculty members from the department of physics currently hold fellow status. Fellow status is a key distinction for faculty to obtain as Kansas State University works toward becoming a top 50 public research university by 2025.

Thumm is being recognized for his work with relativistic calculations for electron-atom collision and the elucidation of interactions of multiply charged ions and photons with atoms, molecules, clusters, surfaces, thin films and carbon nanotubes. This work has been essential to the field. Thumm has collaborated with numerous researchers worldwide and holds several patents. He has published more than 80 original research articles in refereed journals and books, and more than 190 reports and abstracts.

Thumm's current research, conducted at Kansas State University's physics department and J.R. Macdonald Laboratory, models the interaction of very intense and ultrashort laser pulses with matter. These laser pulses allow physicists at a few leading laboratories to follow and control the motion of electrons in atoms, molecules and solids in time. The combination of such laser experiments and theoretical modeling of how laser light interacts with electrons and probes their motion is part of the new research branch called attosecond physics. The field derives its names from the time it typically takes an atomic electron to circle the atomic nucleus -- a few attoseconds, or a few billionths of one billionth of a second.

"Laser technology has been making extraordinary progress in the past decade. It enables us to make stroboscopic pictures of the redistribution of electrons in atoms and molecules," Thumm said. "Experimentals can observe how electrons move in real time; that is, on their natural time scale, tens of attoseconds, and theorists help in understanding these 'electronic movies' by providing computer models, based on quantum mechanical calculations. Attosecond physics promotes our understanding of the dynamics of the making and breaking of chemical bonds and is thus at the very basis of chemistry and, more broadly speaking, life in general."

Thumm joined K-State in 1992. He studied physics and mathematics at the universities of Freiburg and Heidelberg in Germany and in Paris, France. He earned the equivalent of a master of science degree and a doctorate from the University of Freiburg. He has spent sabbaticals at the University of Freiburg, the Max-Planck Institute for Nuclear Physics in Heidelberg and at the Harvard-Smithsonian Center for Astrophysics. Thumm has also organized physicist meetings held at Harvard and Kansas State University.

Law is being recognized for his work with liquid surfaces and the structural phase transitions that can occur on them. He began researching liquids and surfaces as a doctoral student in his native New Zealand. Law began examining a problem that was already regarded as solved related to mixing different liquids and the effect on the surface structure when he arrived at K-State in 1989. He focused on molecules and their adsorption at the liquid-air surface and how that influences the surface composition and their orientation.

"It's sort of what you might call an esoteric subject," Law said. "But unless you understand liquids, you won't understand living things. You're 95 percent water. Liquids are a part of life."

Law discovered that the molecule with the lowest energy covers the surface. But when two molecules have similar energies they then compete for surface sites -- and the surface composition becomes a complex function of their energies. If the molecules' surface orientation is also included, then the situation rapidly becomes extremely complicated. Since the 1970s scientists worldwide had attempted to solve this liquid adsorption problem. Law's group only arrived at a definitive solution around 2000 after more than a decade of research. His selection as a fellow by the American Physical Society is in recognition for this body of research.

Solution of the molecule adsorption problem at liquid surfaces has assisted Law in his latest research on nanoparticles and how they organize on different surfaces. Gold nanoparticles have potential uses in killing cancer cells.

"This ability may well arise due to nanoparticle adsorption at the cell surface, but this is a speculation that needs to be tested," Law said. "If we can solve nanoparticle adsorption at liquid surfaces then we will understand mineral flotation, a multibillion dollar a year process used extensively in the mining industry. Mineral flotation is like magic, it works but no one knows why."

Air bubbles are bubbled through a finely crushed liquid slurry of rock particles. Mineral particles, such as copper, collect at the arising bubble surface and are concentrated in froth above this slurry, similar to beer froth, where they can be skimmed off for further processing. Thus, this process directly involves nanoparticle adsorption at liquid surfaces.

Law received his bachelor's and doctorate degree in physics from Victoria University in Wellington, New Zealand.

Amit Chakrabarti, professor and head of the department of physics, says being named a fellow of the American Physical Society is a big honor and reflects well on the department.

"You must be a top-level physicist to be honored as an APS fellow," he said. "Your work has to have a huge impact on the field. For our department to have eight fellows among current faculty is remarkable."