Optical properties of single crystals of heavy lanthanide chlorides

Studies of heavy lanthanide chlorides may provide important information on the degree of Ln3+–ligand bond covalency. Monocrystals of LnCl3·6H2O, where Ln = Dy, Ho and Er, were grown and spectroscopic investigations were performed at room temperature and at low temperatures down to 4.2 K in order to understand the nature of the Ln3+–L bonds. The intensities of the electronic lines and the Judd–Ofelt parameters were calculated and compared with those obtained for chlorides of light lanthanides (i.e. Ce(III), Pr(III) and Nd(III)). Room temperature Raman and IR studies of the compounds under investigation were also performed. The relationship between hypersensitivity and covalency is discussed. The change of vibronic coupling strength along the lanthanide ion series does not modify monotonically. The ion-pair interactions are especially visible for the 5I8 → 5F2 and 5I8 → 5F3 transitions in the HoCl3·6H2O low temperature spectra.

Spectroscopic investigations of Ln(Dy,Ho,Er)Cl3·6H2O monocrystals at room and at low temperatures down to 4.2 K were adopted to explain the nature of Ln3+–ligand bond. The difference of strength of vibronic coupling along the lanthanide ions series does not change monotonically, just as the nature of Ln3+–L bond. The ion-pair interactions are especially visible for the 5I8 → 5F2 and 5I8 → 5F3 transitions in the HoCl3·6H2O low temperature spectra.Figure optionsDownload as PowerPoint slide