# C. K. Au

## Distinguished Professor Emeritus

RoomPhysics and Astronomy

University of South Carolina

Columbia, South Carolina 29208

(803) 777-2488

## Research Interests

Research in theoretical atomic physics is mainly in the application of quantum theory to simple systems, on the interaction of atoms with photons and the interaction between atoms via the exchange of photons, and on improving perturbation techniques.

It is well known that atoms, though overall neutral, can interact via the van der Waals interaction. In 1948, Cassimir and Polder showed that when quantum electrodynamics is correctly applied, the van der Waals potential falls off according to the seventh power of the distance of separation between the atoms rather than the sixth power in the London form. The London-van der Waals-Cassimir-Polder interaction can be studied for a variety of systems that have an internal structure, not just atoms, and the mediating forces need not be confined to the electromagnetic ones. In the past, this has led to the discovery of many novel effects in both atomic and particle physics. We have also successfully extended our method to include the presence of open-channels.

In most theoretical calculations, perturbation theory is very often employed. An alternative perturbation theory via the logarithm of the wave function has been extensively exploited and applied to various problems of interest, including excited bound states, scattering phase shifts and atomic structure sum rules.

## Selected Publications

- "A Coulomb-Gauge Electrodynamics Analysis of Two Photon Exchange in Electron-atom Scattering," C. K. Au, Physical Review, A 34, 3568 (1986).
- "A Unified Analysis of Multipole and Finite-Mass Corrections in Long-Range Coulombic Interactions," C. K. Au, Physical Review, A 38, 5571 (1988).
- "The Two-Coulomb Exchange Potential in the Presence of Open-Channels," C. K. Au, G. Feinberg, and J. Sucher, Physical Review, A 43, 3419 (1991).
- "Excited Bound State Logarithmic Perturbation Theory Without Nodes," C. K. Au, K. L. Chan, K. D. Chow, C. S. Chu, and K. Young, Journal of Physics, A 24, 3837 (1991).
- "Logarithmic Perturbation Method for the Scattering Phase Shift," C. K. Au, C. K. Chow, C. S. Chu, P. T. Leung and K. Young, Physics Letters, A 164, 23 (1992).
- "An effective scalar photon interaction from ordinary non-relativisic spinless two-body QED," C. K. Au, Physics Letters A 232, 162 (1997).
- "Finite mass effect on two photon processes in hydrogenic systems:Effective scalar photon interaction," C. K. Au and C. S. Chu, Physics Letters A 244, 338 (1998)
- "The van der Waals potential in the presence of weak screening," C. K. Au, Journal of Physics B 31, L699 (1998).