Spectroscopic comparison of UV-VIS electronic transitions of Cr
ions in solution, sol and Xerogel silica matrices
The solgel technologieswere developedduringthe
past 40 years as an alternative for the preparation of
glasses and ceramics at considerably lower temperatures.
The initial systemrepresents a solutionwhere different
polymerization and polycondensation processes
lead to the gradual formation of the solid phase network[
1,2].The first rowtransitionmetal ions[3] have been
utilizedfor thispurpose.The stabilizationenergyofCr3+
ionis amaximuminthe specific typeofoctahedral symmetry
environment,which can be described as a regular
octahedron possessing a centre of inversion. The
strength of the crystal field,?(10Dq), is characterized
bythe energydifference between the 4A2 and 4T2 states.
Figure 1 is theTanabe-Sugano diagramforCr3+which
is verywell known by spectroscopists[4].
Thechromeions areveryinterestingforoptical spectroscopy
and laser physics[5]. For example, Cr3+ in inorganic
glasses is used as an activemediumfor tunable
solid state lasers[6], and sensitizers ofNd-laser[7].Cr5+[8]
and Cr6+[9] have also been shown to be luminescent
even at roomtemperaturewhichmight be interesting
for tunable solidstate lasers inthevisible range.Chrome
ion has been incorporated in the SiO2 network followingasol-
gel routine.Several optical spectroscopic stud-