Transient and persistent spectral holes were burned in the ${}_{}{}^7{}_{}{}^{}F_0^{}{}_{}{}^{}-{}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}$ transition of ${\mathrm{Eu}}^{3+}$ ions in macromonolithic transparent porous nanocrystalline $\gamma$-${\mathrm{Al}}_2$${\mathrm{O}}_3$ produced by sol-gel technology. An unusual temperature dependence of the transient hole width was observed that differs markedly from that in either crystalline or disordered systems. This temperature dependence is explained in terms of Raman processes involving sizeresonant vibrations of the nanoparticles comprising the structure. Possible mechanisms of hole burning are suggested.

• Received 15 April 1996

DOI:https://doi.org/10.1103/PhysRevB.54.R3690