Lanthanides: Luminescence

Abstract

Abstract This chapter encloses a brief historical perspective on luminescence which defines it as a nonincandescent emission. It then extends toward the lanthanide elements, their electronic structure, and how to classify the electronic structure according to the arrangement of the electrons in the 4f subshell. The interaction of light with matter is described both in terms of electronic transitions and vibrational transitions which then allow the introduction of the selection rules that dictates the probability of a transition between two defined states. The luminescence phenomena are rationalized both for an organic chromophore and for a lanthanide ion. The efficiency of the luminescence can be explained by the competition between the radiative relaxation of an excited state and the other deactivations that do not result in the emission of a photon. The sensitization of a lanthanide ion by an organic chromophore is discussed in details thus stressing the importance to describe both ligand‐centered and lanthanide‐centered photophysics. The quantum yields and the lifetimes used to characterize the emissions are then described with rate equations illustrating the importance of the numerous nonradiative relaxation processes. The luminescence of different lanthanide ions are finally related to the electronic levels of different ions, whose energies are quite independent of the chemical environment surrounding the lanthanide ion.