Quantum electrodynamics, time-reversal and parity violation: a relativistic QED approach to atomic and molecular theory

Full text: Usually, relativistic and QED effects are appended to electronic structure calculations of atoms and molecules as perturbations, taking the non-relativistic Schroedinger equation as a starting point. Programs to include relativistic effects in atoms using a basis of four-component Dirac spinors have been available for about twenty years, but the extension of this approach to the study of molecules has been plagued with difficulties, mainly as a consequence of the need to introduce an analytic basis set. We have devised a unified approach to the study of relativistic effects in heavy element chemistry and physics, based on direct solution of the molecular meanfield Dirac equation, with many-body corrections included either by many-body perturbation theory or relativistic density functional theory. A powerful new technique to calculate the Lamb shift in few- or many electron systems has been devised and implemented, eliminating the well-known divergences of QED without the use of regulating parameters. The method has already been applied to the study of many-electron atoms, and, offers considerable promise that it can be extended to calculate two-photon effects in high precision tests of QED. Applications of these methods will be presented, including the study of the magnetic properties of heavy element compounds, theoretical modelling of interferometry experiments designed to detect violations of fundamental time- and parity-reversal symmetries in small molecules, and calculations of the Lamb shift in few electron atomic systems to support experimental tests of the validity of QED. A brief overview will also be given of the technical features of this approach which suggest it as the method of choice in the study of the electronic properties of the heavy elements