Functionalizing Aromatic Compounds with Optical Cycling Centers

Optical cycling, a phenomenon where atoms or molecules quickly emit photons following optical excitation in a repeated cycle, plays a central role in laser cooling and trapping as well as state preparation and measurement. Recent theoretical work [1, 2] suggested aromatic compounds functionalized with a unit of M-O (M = Ca or Sr) for optical cycling can be made suitable for repeated photon scattering. Here, we report the production and characterization of such complexes M-O-R (R = phenyl, naphthyl, and the substituted variants) that have been suggested for optical cycling. We find that all functionalized complexes have diagonal vibrational branching fractions exceeding 90% for the transitions from the two-lowest electronic states to the ground state, which are promising for laser cooling. We describe how the excitation energies of substituted variants follow simple rules that ease their spectroscopic identifications. This work provides a way to utilize chemical functionalization to build molecules of increasing size, complexity, and function for quantum science and technology.



(1) Dickerson, C. E.; et al. Phys. Rev. Lett. 2021, 126, 123002.

(2) Dickerson, C. E.; et al. J. Phys. Chem. Lett. 2021, 12, 3989–3995.