Luminescence Properties of the Lanthanide Ions

Luminescence properties of Ln(III) are reviewed only briefly here. The reader is encouraged to read Chapter 1 for a more detailed treatment. 

The atomic line-like spectra of Ln(III) result from isolation of the inner 4/ orbitals from the surrounding environment by the filled outercore 5 and 5p electrons [14]. Furthermore, electrons in the 4/ orbitals do not participate appreciably in covalent bonding. The lack of interaction of the /-orbitals with the environment or crystal field leads to relatively pure /-orbitals so that selection rules for /-/ transitions are largely adhered to. As a consequence, /-/ transitions in absorbance and emission are weak (e 1 mM cm ) [1,14]. 

A second useful spectroscopic property of Eu(lll) is its relatively long (millisecond) luminescence hfetime [1,19]. This relatively long lifetime is shared by Tb(lll) and Gd(lll). Sueh long lifetimes facilitate experiments that involve time gating of 

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