Abstract
The lowest charge transfer state(CTS)of Eu3+ and,to a lesser extent, of Yb3+ and Tm3+, in Y and La oxysulfides, can be placed in energy by fitting their absorption bands, their emission bands (if present), their feeding behavior into lower rare-earth free-ion-like states, and their role in the sequential quenchings of the activator line emissions with increasing temperature. The CTS is found to be a source, at relatively low temperatures, of free holes which can be trapped for months and then released thermally or with IR irradiation to give the line emissions of the activator. A study of the fraction of CTS excitations which do create free holes as a function of excitation temperature allows determining the bonding energy of the hole to the Eu2+left behind. It is found to be about 1000 cm-1. The binding energy of Eu3+ for a free electron can also be determined. It is found to be near 8000 cm -1. The current knowledge of the CTS is examined and many unanswered questions are raised. Some approaches to exploring these questions are suggested.
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Struck, C.W. and Fonger, W.H., Understanding Luminescence Spectra and Efficiencies Using W and Related Functions, Springer-Verlag, Heidelberg, 1991.
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© 1992 Springer Science+Business Media New York
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Struck, C.W., Fonger, W.H. (1992). Studies of the Charge Transfer States of Certain Rare-Earth Activators in Yttrium and Lanthanum Oxysulfides. In: Di Bartolo, B., Beckwith, C. (eds) Optical Properties of Excited States in Solids. NATO ASI Series, vol 301. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-3044-2_11
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DOI: https://doi.org/10.1007/978-1-4615-3044-2_11
Publisher Name: Springer, Boston, MA
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