FLUORESCENCE QUENCHING OF $Eu^{3+}$ IN SOLUTION VIA ENERGY TRANSFER TO THE VIBRATIONAL OVERTONES OF THE SOLVENT

Abstract

The fluorescence efficiency of $Eu^{3+}$ in various organic solvents depends upon the concentration of such groups as -OH, $\rightarrow$ $CH, -OD$ and $\rightarrow C-D$. Solvents used include such pairs as ($CH_{2}CO$)$_{2}O:CH_{3}COOH$, ($CH_{3}CO)_{2}O:CH_{3}COOD$, $CH_{3}COOD:CH_{3}COOH$, $CF_{3}COOH:CH_{3}COOH$, $CCl_{3}COCl:CCl_{3}COOH$ etc. The composition of the solvent is varied in such a way so that the concentration of the most powerful quenching group is altered to a small extent (up to 10\%) whereas the rest of the properties of the solvent remain unchanged. The quenching efficiency is discussed in terms of energy transfer from the lowest excited state of $Eu^{3}$ ($^{5}D_{o}$) to the vibrational overtones of the groups under consideration. Both absorption and emission spectra were taken to eliminate any effects upon the electronic structure of $Eu^{3}$+ due to drastic changes in the properties of the solvent.