A. Bouajaj et al., OPTICAL SPECTROSCOPY OF EU3-DOPED SILICA-GELS(), Philosophical magazine. B. Physics of condensed matter. Structural, electronic, optical and magnetic properties, 71(4), 1995, pp. 633-640
Laser techniques have been applied to study the spectroscopy of Eu3+ i
n silica gels. Site selection spectroscopy, resonant fluorescence line
narrowing and lifetime measurement show a continuous evolution of the
system as a function of the thermal treatments which produce the gel-
to-glass transition. Two different environments for the Eu3+ ion, a li
quid-like and a dry environment, have been observed during the initial
steps of the dehydration process. At heat treatments below 250 degree
s C the non-radiative relaxation channels due to coupling with the O-H
vibrational modes are very efficient. As the densification continues,
clustering of Eu3+ induces strong energy transfer also at a relativel
y low concentration of the rare-earth ions. Site selection by laser ex
citation is indeed efficient only for non-densified samples. Dynamic i
nteractions are site dependent as shown by the temperature dependence
of the homogeneous linewidth taken at different energies within the D-
5(0) <-> F-7(0) line.