PM: Atomic Physics Investigations of Rare Earth Elements: A Prologue to New Physics Beyond the Standard Model

This award supports the investigation of cerium (Ce) and terbium (Tb) as prospective candidates for next generation optical atomic clocks and laser cooling. Atomic clocks have been instrumental in the advancement of science and technology in the twentieth century, leading to innovations such as global positioning, advance communications, and tests of fundamental particle physics.

A next generation optical atomic clock would extend the capabilities of these systems and will enable a renaissance of timing applications such as enhanced security for data routing and communications, advanced earth and space time-based navigation, geophysical surveying, testing Einstein's Theory of General Relativity, and searches for variations in the fundamental constants of the universe. Laser cooling is a technique that utilizes the mechanical action of light to reduce the velocity of an atom in a gas.

The use of lasers to cool atoms opened up new frontiers in physics ranging from the formation of new states of matter to enabling emerging quantum technologies. The goal of this project is the extension of laser cooling to the proposed atomic species to enable additional experimental discovery platforms to facilitate new scientific explorations to address fundamental physics questions related to dark matter searches and the composition of the universe.

More specifically, this project will investigate the atomic physics properties and implement laser cooling of Ce and Tb for their potential uses as next generation time/frequency standards and as ultracold ensembles with unique properties and dynamics. The project will involve minority graduate, undergraduate, and high school students via existing University of Alabama-Birmingham programs to participate in research projects in the Simien Spectroscopy and Laser Cooling group.

Additional outreach activities will aim to get K-12 students interested in science and engineering by performing physics and chemistry demonstrations at local schools in the region.

This project is an experimental research program directed towards investigating spectroscopic, laser cooling, and collisional properties of atomic cerium and terbium as it relates to optical clocks, variation in fundamental constants for new physics searches beyond the Standard Model, and dipolar quantum gases. These atoms have exotic electronic configurations and large ground state magnetic moments that allows them to have submerged shell optical clock transitions that are sensitive to variations in the fine structure constant alpha, and exotic quantum gas phases with phenomenon dominated by dipole-dipole interactions.

In particular, the spectroscopic studies will involve measurements of the hyperfine structure, isotope shifts, and radiative lifetimes of strong electric dipole and spin-forbidden transitions. The objective of this study is to determine Ce and Tb hyperfine constants, isotope shifts, and natural linewidths and lifetimes. The hyperfine constants define the ordering of the hyperfine peaks and contributions to the energy shifts from the magnetic dipole and electric quadrupole interactions.

The isotope shifts are small deviations in the transition energies due to differences between masses and the volumes of the nuclei. The natural linewidths and lifetimes are associated with transition rates. The determination of these spectroscopic properties are necessary for implementing laser cooling and trapping of cerium and terbium.

Furthermore, Ce and Tb will be laser cooled as a first step towards performing precision measurements and studying atomic dipolar physics. In addition, measurements of collision quenching cross sections, pressure broadening, and frequency shifts will occur inside an atomic vapor cell. These quantities will characterize the collision sensitivity and give insight into the combined action of electron screening and configurational interactions of the proposed Ce and Tb laser cooling and optical clock transitions.

This study will help determine the effect of collisions on the accuracy of cerium or terbium as a frequency standard. This project is funded by the Atomic, Molecular and Optical Experimental Physics program, the Established Program to Stimulate Competitive Research (EPSCoR), the Experimental Particle Physics program, and the Experimental Nuclear Physics Program.

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.