Some new aspects of lanthanide optical spectroscopy: circular dichroism and two-photon absorption

It has been shown that circular dichroism (CD) and two-photon absorption (TPA) spectroscopies are capable of throwing new light on fn⇒ fn optical transitions. High-resolution circular dichroism of single crystals can provide information on the chiral environment as well as on the magnetic and electric quadrupolar transition moments of lanthanide ions, and thus can be exploited for the purpose of assignment of bands. TPA, on the other hand, although capable of resolving crystal-field components better than one-photon absorption, exhibits puzzling intensity features, which need to be sorted out before it can be generally used as a diagnostic tool