This research program, located at an undergraduate institution, involves table-top experiments with lasers and atoms to gain insights into the so-called "Standard Model of particle physics" that is typically studied by physicists at large particle accelerator facilities. In the present work, properties of the metal atoms thallium and indium are measured to very high accuracy. Results are then compared to state-of-the-art theoretical calculations of these same properties, as high-quality tests of the fundamental physics phenomena probed by these measurements rely critically on the combination of precise experimental results reinforced by accurate, independent atomic structure calculations. Students become involved in all aspects of the experimental work, designing and testing laser, optical, and signal processing systems, and carrying out data collection and data analysis procedures.

Over recent decades, highly-precise atomic physics experiments using lasers have contributed important insights into the physics of the Standard Model of particle physics. Such low-energy physics tests complement accelerator-based experimental work. The small size of these effects demands very high precision, extensive study of systematic errors, and careful experimental design. Also, the size of these manifestations of high-energy physics in atoms scale dramatically with Z, the atomic number, suggesting the use of very heavy (and therefore complicated) atomic systems. Yet in order for these measurements in heavy atoms to provide unambiguous tests of the Standard Model, equally precise atomic theory models of the atomic wavefunctions are required to distinguish the ordinary quantum mechanical behavior from the "exotic" particle physics phenomena being targeted. The PI and his students are continuing with an ongoing series of diode laser spectroscopy measurements of the atomic properties of Group IIIA atoms (thallium, indium) which can be compared to state-of-the-art atomic theory calculations. They study atoms both in heated vapor cells as well as a dense, collimated atomic beam apparatus. These atoms contain three valence electrons, challenging the approximation techniques required to accurately compute wavefunctions. This experiment-theory interplay has resulted in significantly improved accuracy in recent years, and therefore improved atomic-physics-based tests of fundamental particle physics processes in these heavy atomic systems. In the longer term, the group is planning to perform a new experiment to measure the Weak Interaction in an atomic beam of thallium atoms, using its parity-violating optical rotation signature, improving upon an experimental result by a group that included the PI some years ago.

National Science Foundation (NSF)
Division of Physics (PHY)
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John D. Gillaspy
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Williams College
United States
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