RUI: Driving Forbidden Vibrational Overtones in Trapped Molecular Ions

Amherst College, Amherst MA

Investigators

Abstract

Some atoms and molecules have quantum states with properties that are particularly well-suited for timekeeping, for quantum information processing, or for tests of physical laws. This project focuses on molecular vibrations that are sensitive to fundamental constants such as the electron mass and the proton mass. These vibrations occur when atomic nuclei stretch and compress a chemical bond, and their vibration frequencies depend on the proton-to-electron mass ratio. This team will conduct a proof-of-principle experiment using vibrational states to search for time dependent changes in fundamental constants. Such changes are predicted by some models of quantum gravity or dark matter, but have not yet been detected experimentally. This project promotes the progress of science by developing new ways to study molecular vibrations as precision tests of fundamental physics. This research takes place at a liberal arts college where undergraduate students are involved in all aspects of the work. In addition to training the next generation of scientists, this work develops skills in experimental physics that are transferable to a wide array of future endeavors. This project will investigate electric-dipole-forbidden vibrational overtones in trapped molecular ions. The team will drive an overtone as a two-photon transition in the diatomic oxygen molecular ion, which is of long-term interest as both an optical molecular clock and as a probe for time-variation of the proton-to-electron mass ratio. The nonpolar nature of the molecule suppresses systematic shifts related to electric fields, such as AC Stark shifts and blackbody radiation. A key tool for this work is a stable optical local oscillator that is referenced to a separate optical clock. To demonstrate the promise of this system, this team will reduce the uncertainty on an overtone transition frequency by several orders of magnitude and monitor it over the course of a year. 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.