Line broadening studies for Cr3+ pairs and single ions in different oxide lattices

The electron-phonon coupling for Cr3+ in different oxide host lattices (MgO , alpha -Al2O3 and LaAlO3) was probed by performing temperature dependent l ine broadening measurements for zero-phonon emission lines of single ions a nd exchange coupled pairs. No differences in electron-phonon coupling were found comparing the results for pairs and single ions in alpha -Al2O3 (3NN and 4NN pairs) and LaAlO3 (NN pairs). In Cr3+ doped MgO (Cr3+-V-Mg-Cr3+ pai rs), it was found that the electron-phonon coupling strength parameter or i s larger for the pairs than for the isolated Cr3+ ions. This is probably du e to changes in the surroundings of Cr3+ by local charge compensation by a magnesium vacancy, and not to interaction between the Cr3+ ions.