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Functionalizing aromatic compounds with optical cycling centres


Molecular design principles provide guidelines for augmenting a molecule with a smaller group of atoms to realize a desired property or function. We demonstrate that these concepts can be used to create an optical cycling centre, the Ca(I)–O unit, that can be attached to a number of aromatic ligands, enabling the scattering of many photons from the resulting molecules without changing the molecular vibrational state. Such capability plays a central role in quantum state preparation and measurement, as well as laser cooling and trapping, and is therefore a prerequisite for many quantum science and technology applications. We provide further molecular design principles that indicate the ability to optimize and expand this work to an even broader class of molecules. This represents a great step towards a quantum functional group, which may serve as a generic qubit moiety that can be attached to a wide range of molecular structures and surfaces.

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Fig. 1: 2D and DLIF spectra of CaO-Ph-3,4,5-F3.
Fig. 2: Vibrational decay ratios for all observed modes.
Fig. 3: pKa trends.

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Data availability

The experimental datasets and codes for Figs. 13 and Extended Data Fig. 1 are available as source data and from the online Zenodo repository at Other data supporting the findings of this study are available in the Supplementary Information. Source data are provided with this paper.


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We thank T. C. Steimle for sharing critical equipment and for useful discussions and also N. Vilas and Y. Bao for helpful discussions. This work was supported in part by the National Science Foundation (grants nos. PHY-1255526, PHY-1415560, PHY-1912555, PHY-2110421, CHE-1900555, DGE-1650604, DGE-2034835 and OMA-2016245), the Army Research Office (grants nos. W911NF-15-1-0121, W911NF-14-1-0378, W911NF-13-1-0213, W911NF-17-1-0071 and W911NF-19-1-0297), AFOSR (grant no. FA9550- 20-1-0323) and the US Department of Energy, Office of Science, Basic Energy Sciences (award no. DE-SC0019245).

Author information

Authors and Affiliations



A.N.A., W.C.C., J.R.C., J.M.D. and E.R.H. conceived the idea. D.M., B.L.A. and Z.D.L. constructed the vacuum, cryogenic and spectroscopic apparatus under the supervision of J.M.D. G.-Z.Z. and G.L. explored the initial production method. G.-Z.Z., D.M. and Z.D.L. acquired all the experimental data. C.E.D. performed all calculations. Z.D.L., D.M. and M.J.F. built the Pearson function to fit peaks in all DLIF spectra. G.-Z.Z. and D.M. analysed all data, with useful contributions from B.L.A., Z.D.L., W.C.C. and E.R.H. G.-Z.Z., D.M. and E.R.H. prepared the manuscript with contributions from all authors. The research was coordinated by W.C.C., J.M.D. and E.R.H.

Corresponding author

Correspondence to Eric R. Hudson.

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Nature Chemistry thanks Jinjun Liu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 2D and DLIF spectra of all other five molecules.

a-c, CaO-Ph. d-f. CaO-Ph-3-CH3. g-i, CaO-Ph-3-F. j-l, CaO-Ph-3-CF3. m-n, CaO-Ph-3,4-F2. In the 2D spectra, the orange dashed lines mark features due to CaOH or CaF, while the green dotted lines indicate features from CaO-Ph-X species. In the corresponding dispersed LIF spectra, the experimental curves (black) are fitted with Pearson functions (red). The blue sticks illustrate the vibrational branching ratios of different vibrational modes. The assignments of resolved vibrational peaks are also given. The symbols * and + indicate features due to CaOH and Ca, respectively.

Source data

Supplementary information

Supplementary Information

Supplementary discussions of curve fitting and error analysis, Tables 1–11 and Figs. 1 and 2.

Source data

Source Data Fig. 1

Datasets of 1D and 2D spectra and Pearson fitting codes.

Source Data Fig. 2

Data and Matlab codes.

Source Data Fig. 3

Data of Fig.3 in excel.

Source Data Extended Data Fig. 1

Datasets of 1D and 2D spectra.

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Zhu, GZ., Mitra, D., Augenbraun, B.L. et al. Functionalizing aromatic compounds with optical cycling centres. Nat. Chem. 14, 995–999 (2022).

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