Elucidating Ultranarrow 2F7/2 to 2F5/2 Absorption in Ytterbium(III) Complexes

25 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Achieving ultranarrow absorption linewidths in the condensed phase could enable optical state preparation of specific non-thermal states, a prerequisite for quantum-enabled technologies. The 4f orbitals of lanthanide(III) complexes are often referred to as “atom-like”, reflecting their isolated nature, and are promising substrates for the optical preparation of specific quantum states. To better understand the photophysical properties of 4f states and assess their promise for quantum applications, theoretical building blocks are required for rapid screening. In this study, an atomic-level perturbative calculation (spin-orbit crystal field, SOCF) is applied to various Yb(III) complexes to investigate their linear absorption and emission through a fitting mechanism of their experimentally determined transition energies and oscillator strengths. In particular, the optical properties of (thiolfan)YbCl(THF) (thiolfan = 1,1′-bis(2,4-di-tert-butyl-6-thiomethylenephenoxy)ferrocene), a recently reported complex with a ultranarrow optical linewidth, are computed and compared to those of other Yb(III) compounds. Through a symmetry descent procedure and a transition energy sampling study, major contributors to the optical linewidth are identified. We find that low-symmetry crystal fields, combined with the ultra-high similarity of states resulting from an anisotropic crystal field, create particularly isolated f-f transitions and narrow linewidths. Simultaneously, we find that these atom-like transitions have highly correlated excited-ground energy fluctuations that serve to greatly suppress inhomogeneous line-broadening. This article illustrates how SOCF can be used as a low-cost method to probe the influence of symmetry and ligands on the optical properties of Yb(III) complexes to assist the development of novel lanthanide series quantum materials.


Ultranarrow Linewidth
Crystal Field
Quantum Science
Ytterbium Complex
Local Charges
Symmetry and Anisotropy
Fluctuations and Linewidth
4f-to-4f Transitions

Supplementary materials

Supporting Information: Elucidating Ultranarrow 2F7/2 to 2F5/2 Absorption in Ytterbium(III) Complexes
1. Spin-orbit and crystal field effects acting on 4f orbitals; 2. Magnetic dipole (M1) transition oscillator strength; 3. Judd-Ofelt treatment of 5d mixing and electric dipole (E1) transition; 4. 3-Stage fitting mechanism (rigid-bond rotation and charge samplings); 5. Full spectral calculation table; 6. Atomic similarity factor γ; 7. Crystal field splits for lowest 2 ground and excited SO states in Yb complexes; 8. Single charge fluctuation model and all-charge-moving model.


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