Transient hole-burning and homogeneous linewidth of Eu3+ in sol–gel-produced corundum

In α-Al2O3, small-grain ceramics prepared by annealing of sol–gel-produced γ-Al2O3, it is possible to obtain trivalent rare earth ions at a single regular site despite the large difference in RE3+ and Al3+ ionic radii. Transient spectral holes, generated by a redistribution of the population among the hyperfine levels of the two isotopes of Eu3+, were burned in the inhomogeneously broadened lineshape of the 7F0–5D0 transition of Eu3+. This observation gives additional evidence for the regular structure of Eu3+ centers in small-grain corundum ceramics. The temperature-dependent hole broadening probably results from dephasing of electronic states by two-phonon Raman processes. The results are discussed together with earlier non-resonant fluorescence line narrowing results on the 5D0–7F1 transition, obtained by single frequency excitation of the 7F0–5D0 transition.