Can magnetic circular dichroism tackle the problem of site symmetry in solutions?

Magneto-optical investigations of rare earth doped sol–gel derived silicate xerogels

“…7). Since the MCD signal of the 7 F 0 -5 D 2 transition at 464 nm is twice as intense as the MCD signal of the 7 F 0 -5 D 1 MD transition at 525 nm, this is consistent with a coordination symmetry around the Eu 3 þ ions close to D 3h [18].…”

“…1) have confirmed the presence of the Si-O-Si structural units right from the xerogel [19]. A small degree of cross-linking in the structure is reflected by the narrow 7 F 0 -5 D 0 luminescence, indicating that the Eu 3 þ ion occupies a smaller range of sites [18]. Some water is still present in the xerogel in the form of un-condensed hydroxyl (OH À ) groups.…”

“…going from a D 3h symmetry to a C 4v symmetry, the crystal fields induce a sign change of the MCD signal from a negative to a positive one through the odd crystal field component), while the 7 F 0 -5 D 1 transition can be used as a sign reference transition [3,16]. According to the simulation of the MCD spectra in different symmetries the MCD signal of the 7 F 0 -5 D 2 ED transition is twice as intense as the MCD signal of the 7 F 0 -5 D 1 MD transition in the D 3h symmetry and they are equal in the case of the C 4v symmetry [18]. The other ED transitions do not change their sign but the intensities of the MCD signals increase depending on the site symmetry.…”