This project supports the latest in a series of laser-based measurements of the electronic atomic structure of a set of particular heavy metal atoms, including thallium, indium, lead, and tin. The goal is to measure, with unprecedented precision, properties of these atoms by using lasers to cause electrons in the atom to "jump" from one quantum level to another. In a long-standing collaboration, the investigators will compare their high-precision measurements of atomic properties to the predictions by colleagues who perform complex theoretical calculations based on the quantum mechanical properties of these atoms. This interplay of experimental measurements and first-principles theoretical predictions reflects the process by which science should ideally progress: better experiments test current models and assess their accuracy while new theoretical techniques and predictions inform what additional experiments should be undertaken. The work in this atomic physics laboratory involves building and testing laser and optical systems, constructing and optimizing electronics and control systems, using computer-based methods to collect and then model and analyze large amounts of data. This work is located at an undergraduate liberal arts institution (Williams College) where students at all levels of their education become research partners, contribute to all aspects of the experimental work, collaborate on presentations at conferences and journal publications, and in many cases go on to graduate work in physics, engineering, and related fields. NSF funding also supports the hire of a postdoctoral research associate who will work closely with the Principal Investigator and undergraduates, receive important mentoring, and become involved in the department's educational life. The most recent NSF-funded postdoc will be departing the group this summer to begin a tenure-track faculty position at another nearby undergraduate institution, Connecticut College. Training of the next-generation of science and engineering students, as well as future faculty members and teachers, is thus a central aspect of the supported research project.
This research program, located at an undergraduate institution, focuses on high-precision measurements of atomic structure in complex, multi-valence-electron systems using diode laser spectroscopy techniques. In addition to providing exacting tests of state-of-the-art ab initio atomic theory, these atomic systems play an important role in tests of fundamental physics, including searches for violations of discrete symmetries. These searches rely on accurate, independent atomic structure calculations, which are needed to distinguish the complicated (but "ordinary") quantum mechanical effects from the fundamental particle physics being tested. Recent work has focused on vapor-cell and atomic-beam-based spectroscopy of tri-valent indium and thallium where recent precise polarizability results have helped guide the latest theory work by distinguishing between two complementary approximation techniques. Current work focuses on transition amplitude measurements in four-valence lead, where new ab initio calculations have substantially improved calculational accuracy. This work utilizes a very-high-precision Faraday polarimetry technique to observe, for the first time, an electric quadrupole transition amplitude in the ground state configuration of lead. Given existing high-precision parity nonconservation measurements in lead and thallium, modest improvements in atomic theory precision can have significant impact on the quality of these atomic-physics-based tests of electroweak physics. In the course of this work, new techniques for laser stabilization, small-signal detection, and precision polarimetry will continue to be developed that have broad applicability. All of this work provides research-training opportunities for undergraduate students at every stage of their education, many of whom grow to become research partners, coauthor papers and conference presentations, and go on to attend highly selective Ph.D. programs in physics and related disciplines.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
