Impurity-Trapped Exciton States of Lanthanides in Solids

Altogether, impurity states and impurity-trapped excitons define the realm of lanthanide activated solid-state materials. This is a realm where experiment and theory should meet but where the research work conducted is overwhelmingly experimental. Their structure and optical properties are complex and rich. They are a genuine challenge for quantum chemists. What is needed is not massive production of theoretical results, which follow experiments (which, in any case, would probably be very difficult to attain, given the pace of experimental work and sophistication of the theoretical methods apphcable). What is needed is to answer basic questions that cannot be answered by experimental techniques alone so that their electronic structures are mastered beyond simple model and beyond empirical model descriptions, to the point where the intensive and constant search for new materials could count on the ability to predict, which is characteristic of ab initio quantum chemical methods when it is found how to stretch them to the limits of their capabilities. 

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