Optical Excitation of Luminescence and Energy Transfer

One observes, a strong broad absorption spectrum in the UV part of the spectrum as the excited 5d state of the Eu ion is split by ligand field interaction with the oxygen ions surrounding it. 

The excitation spectrum of the Mn spectrum in BaMgAlioOi7 Eu,Mn is, in the UV, very similar to the excitation spectrum of the compound without Mn. This is an example of Eu -sensitized emission of Mn, as proven by the similarity of the excitation spectrum of both the Eu and the Mn emission. The very localized excitation (exciton) of Eu is transferred to the Mn ion. The energy transfer process might involve more than one Eu ion (excitonic energy transfer via the Eu sublattice). 

It has to be noted that the emission spectrum depends on the Sb and Mn concentrations. By adjusting these concentrations, the color of the emission can be varied. 

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