Grant: Discovery Grants Program - Individual

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. One of the most exciting areas of modern atomic physics is the possibility that such high precision probes will yield evidence for new physics beyond the standard model, or at least extend the limits of what can be learned from high energy particle accelerators. We particularly focus on relatively simple atomic systems containing two or three electrons, such as helium and lithium. For such systems we have developed specialized methods for the calculation of nonrelativistic wave functions and energies that are essentially exact for all practical purposes. On this firm foundation we build relativistic, finite nuclear mass, and quantum electrodynamic (QED) corrections up to the limits of current knowledge. A comparison with high precision measurements of atomic transition frequencies at other laboratories around the world then yields well-defined differences that can be attributed, in the first instance, to nuclear properties such as the the nuclear charge radius or the Zemach magnetization radius. This method has been shown in previous work to provide a unique measurement tool for short lived nuclear species such as He-6 and Li-11 that are not accessible by other methods of nuclear physics. In other cases, a residual discrepancy between theory and experiment may provide evidence for new physics beyond the standard model, such as dark matter. The results have been published in top journals such as Phys. Rev. Lett. and Science. In brief, future work will include (1) theory of the tune-out frequency for metastable helium, in collaboration with measurements at the Australian National University to provide a unique new test of QED; (2) proposal to search for an electron-neutron interaction from anomalies in the atomic isotope shift (King plot) as evidence for dark matter in the form of light bosons; (3) new high-precision theoretical methods to cover the unexplored territory of highly excited Rydberg states of atoms; (4) theory of atomic electrons ejected following the beta-decay of the nucleus to search for new physics beyond the standard model in the angular correlations. All of these projects are motivated by close interactions with experimental programs elsewhere. They involve a combination of high-precision computing with theoretical analysis and extensions of existing theory. They therefore provide an ideal training ground for students. They are all built on the unique technology we have developed for solutions to the quantum mechanical few-body problem that are essentially exact for all practical purposes.  In many cases our results set a new standard for accuracy, and are the most accurate in the literature.