Fully saturated hydrocarbons as hosts of optical cycling centers

TL;DR

This paper proposes design principles for larger saturated hydrocarbon molecules as optical cycling centers, enabling their use in quantum technologies by ensuring robust, closed optical transitions.

Contribution

It introduces two novel design principles for creating larger molecules with optical cycling centers, expanding the scope of molecules suitable for quantum applications.

Findings

Larger saturated hydrocarbons can serve as effective ligands due to their HOMO-LUMO gap.

Electron-withdrawing groups can improve Franck-Condon factors without disrupting molecular structure.

Larger molecules can sometimes have higher FCFs than smaller counterparts.

Abstract

Designing closed, laser-induced optical cycling transitions in trapped atoms or molecules is useful for quantum information processing, precision measurement, and quantum sensing. Larger molecules that feature such closed transitions are particularly desirable, as they extend the scope of applicability of such systems. The search for molecules with robust optically cycling centers has been a challenge, and requires design principles beyond trial-and-error. Here, two design principles are proposed for the particular architecture of M-O-R, where M is an alkaline earth metal radical, and R is a ligand: 1) Fairly large saturated hydrocarbons can serve as ligands, R, due to a substantial HOMO-LUMO gap that encloses the cycling transition, so long as the R group is rigid. 2) Electron-withdrawing groups, via induction, can enhance Franck-Condon factors (FCFs) of the optical cycling transition, as long as they do not disturb the locally linear structure in the M-O-R motif. With these tools in mind, larger molecules can be trapped and used as optical cycling centers, sometimes with higher FCFs than smaller molecules.