Knowledge Bank

$Sncl4$ OF $Tb3+$ in $pocl3$ The fluorescence emission of $Tb3+$ arising from the $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}D4$ - state in $POC13:SNcL4$, measured at 490, 545 and 585 nm, is slightly enhanced relative to that in protic” solvents. The dependence of the aforementioned fluorescence intensity upon the concentration of the ion is negligible although its dependence upon the temperature is significant. On the other hand fluorescence emission from the second excited state of $Tb^{3+}$, i.e., the $^{5}D_{3}$ - state, depends drastically upon both the $Tb^{3+}$ concentration and the temperature, Fluorescence emission arising from the $^{5}D_{3}$ - state, measured at 385, 415, 438, 456 and 472 nm, has -not been previously observed in solutions of $Tb^{3+}$ using either protic” solvents or any other solvent in general, A four-fold increase in this fluorescence intensity is attained by lowering the concentration of $Tb3+$ by a factor of ten, whereas a twenty-fold increase is observed by lowering the temperature from $55\circ C$ to $-15\circ$C. Similar concentration and temperature effects were observed upon the lifetimes of the fluorescence emission arising from both excited states. Since the absorption spectra of $Tb3+$ in $P0C13:SnC14$ are almost temperature and concentration independent, the observed effects are attributed to the $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}D3\to 5D4$ - radiationless transition by both intermolecular energy transfer to $Tb3+$ ($\mathrm{<mrow\; data-mjx-texclass="ORD">7</mrow>}F6$) and electronic-vibrational energy transfer to vibrational excited states of the solvent.