An Optical Molecular Clock for New Physics Searches

Some vibrational transitions in molecules have the potential to serve as optical clocks or as probes for new physics.[1] The vibrational overtones in homonuclear molecules such as O₂⁺ are electric-dipole forbidden and thus intrinsically narrow and immune from some systematic shifts.[2] Here, we present our progress towards investigations of these transitions in an ion trap. Photoionization from a pulsed molecular beam allows loading of vibrationally selected molecular ions. Co-trapping with atomic ions provides sympathetic cooling. Molecular state detection is from dissociation followed by identification of the resulting atomic ions. We will describe production of O⁺ ions with multi-photon dissociation at 266 nm. Current experiments focus on two-photon spectroscopy at optical wavelengths.

[1] D. Hanneke, B. Kuzhan, A. Lunstad, Optical clocks based on molecular vibrations as probes of variation of the proton-to-electron mass ratio, Quantum Science and Technology 6, 014005 (2021)

[2] R. Carollo, A. Frenett, D. Hanneke, Two-Photon Vibrational Transitions in ¹⁶O₂⁺ as Probes of Variation of the Proton-to-Electron Mass Ratio, Atoms 7, 1 (2018)