Site selection spectroscopy of SiO2:Eu3+ gels

Silica gels doped with Eu3+ ions were studied at temperatures between 10 K and 300 K by site selection spectroscopy in samples heated up to 200°C. The 5D0 -> 7F0 transition shows internal structures due to the different environments of the europium ions. Lifetimes, energy levels and homogeneous linewidths are site dependent. In the wet gel the Eu3+ ions prefer a liquid-like environment and only when the liquid is removed by heat treatment, the ion is linked more strongly to the silica network.