At low-temperatures, cooling from anti-Stokes emission loses efficiency because of thermal depopulation of the upper Stark levels.
By considering the 2F7/2 excited state, we have estimated the positions of all emissions from the 2D ground state to the 2F7/2 Stark levels.
The consistency between the two sets of data is reasonable, and the calculated irreducible representations of the Stark levels reflect the polarization behavior of the corresponding transitions (Figure8).
To determine the decomposition of Stark levels stemming from 2F5/2 and 2F7/2 multiplets, Watterich et al.[8] used a polarized emission spectrum of cerium in YAB realized at 4 K (Figure7).
Knowing the symmetry site occupied by an ion in a given crystal, the group theory allows us to determine the number and symmetry of the Stark levels stemming from every multiplet 2S+1L J.
This spectrum is badly resolved, and it shows the contribution of 2F5/2 and 2F7/2 multiplets, corresponding to transitions from the 5d1 fundamental state to the F1, F2, F3, F4, F5, F6, and F7 Stark levels stemming from 4f1 configuration.
Variable-temperature magnetic susceptibility measurement reveals that multi-bridging fashion of carboxylic group in 1 results in depopulation of the stark levels for a single Gd III) ion and/or possible antiferromagntic interactions between adjacent Gd III) cations within the carboxylato bridged binuclear unit.
The crystal field strength parameters are defined by [31] N V = ∑ k, q 4 π 2 K + 1 B q k 2 1 / 2, where B q k is the crystal field parameters that affect the Stark levels of Er3+, which characterize the interaction between ligands and the central ions and include the radial integral of the wavefunction.
By considering the decomposition of 4f and 5d configurations under the influence of spin-orbit coupling and crystal field effect, we expected only five lines corresponding to transitions from the 2F5/2 (fundamentalntal state and the five Stark levels stemming from 2D3/2 and 2D5/2 multiplets.
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