Understanding the luminescence of rare-earth-doped crystals through electron paramagnetic resonance spectroscopy

Optical transitions of rare-earth ions in condensed matter, even at very low doping levels, often exhibit complex structures in absorption and emission spectra. These extra transitions can be due to different rare-earth ions sites or due to interacting ions. Electron paramagnetic resonance spectroscopy of Kramers’ ions is a powerful tool to analyze this multisite character. Moreover, it can give information about the interactions between two rare-earth ions in pairs. We illustrate these different points with some results obtained in our group with vanadates crystals and with a general analysis of rare-earth pairs spectra in single crystals.