Energy Level Diagrams for the Lanthanide Ions, and their Electronic Spectra

3 Energy Level Diagrams for the Lanthanide Ions, and their Electronic Spectra 

Most lanthanide ions absorb electromagnetic radiation, particularly in the visible region of the spectrum, exciting the ion from its ground state to a higher electronic state, as a consequence of the partly filled 4f subshell. The f-f transitions are excited both by magnetic dipole and electric dipole radiation. Normally the magnetic dipole transitions would not 

Not all the lanthanide ions give rise to f-f transitions, including obviously the f and f species, La + and Lu +. Likewise there are no f-f transitions for the f (Ce +) and f(Yb +) ions, as with only a single L-value there is no upper 4f state. Transitions between Fs/2 and Fv/2 are seen in the case of Ce + as a rather broad band in the infrared region around 2000 cm Ce + and Yb +do, however, give rise to broad 4f 4f 5d transitions (as indeed do many lanthanides). Even an ion like Eu +, which has several absorptions in the visible region of the spectrum, has only weak absorptions, so many of its compounds appear colourless the only three tripositive ions whose compounds are invariably coloured are Pr +, Nd +, and Er +. 

Colours of the Ln + ions in aqueous solution are listed in Table 5.2. A typical spectrum is that of Pr +, shown in Eigure 5.4 note the sharp absorption bands, with extinction coefficients below unity. 

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Energy Level Diagrams for the Lanthanide Ions, and their Electronic Spectra Table 5.1 Magnetic Moments of Ln + ions at room temperature... 

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