Theory of atomic processes and interactions

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The unifying theme of this proposal is the development of new measurement tools through the combined application of both high precision theory and experiment to atoms. Two examples are a significant new value for the fine structure constant, which is one of the fundamental constants of nature, and table-top measurements of the size of exotic atomic nuclei. Recent successes at Argonne (U.S.), GSI (Germany) and TRIUMF (Canada) have focused on the so-called neutron-rich "halo" nuclei with extra planetary neutrons, such as He-6. The significance of the results is that they enable one to distinguish amongst the various theoretical models proposed for the effective forces holding the nucleus together. By studying structures that fall apart easily, we learn about the forces holding them together. A fascinating new project for the future involves a search for new physics beyond the standard model of elementary particles, as revealed by angular correlations following beta decay of the halo nucleus. Two recent advances have made these initiatives possible. First, our work has yielded unprecedented levels of accuracy in calculating the properties of atoms from first principles. Some of this requires the high performance computing facilities of SHARCNET, together with fundamental advances in methods to calculate essential corrections due to relativity and quantum electrodynamics. I have formed an international collaboration of other researchers in Canada and China to carry out this work, with the help of dedicated resources from SHARCNET. Second, we work in close collaboration with the top experimental groups around the world who perform measurements of exquisite accuracy and sensitivity. The ability to trap and study just a single atom plays a key role. A long sequence of joint papers published in Physical Review Letters has resulted from these collaborations. Our theoretical results dominate the literature in this area, and they are providing the motivation for several experimental groups around the world to advance the state-of-the-art for high precision laser metrology.