ELECTRONIC EXCITATION ENERGY TRANSFER MECHANISMS BETWEEN $Tb^{3+}$ and $Eu^{3+}$ IN DMSO
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Date
1974
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Ohio State University
Abstract
Light excitation of mixture of $TbC1_{3}$ and $EuC1_{3}$ in DMSO using spectral regions in which both components absorb light, namely at $345 \pm 1$, $353 \pm 1$, $362 \pm 1$ and $371 \pm 1 $nm, is accompanied by a reduction in the fluorescence intensity of $Tb^{3+}$ measured at 488 and/or 543 nm, as well as by an enhancement in the fluorescence intensity of $Eu^{3+}$, measured at 591 nm. Electronic excitation energy transfer appears to originate predominantly from the $^{5}D_{4}$ - state of $Tb^{3+}$, and it is independent of the excitation wavelength- The average rate constant for the excitation energy transfer la $1.50 \times l0^{3}M ^{-1}1sec^{-1}$. Electronic energy transfer originating from the $^{5}D_{3}$ - state of $Tb^{3+}$ was not observed, possibly due to a rapid $^{5}D_{3} \rightarrow ^{5}D_{4}$ - radiationless process. The rate constant of this latter process is associated with a lower limit of about $10^{5}sec^{-1}$ The value of $1.50 \times 10^{3}M^{-1}$ $sac^{-1}$ for the transfer rate constant is much smaller than the value expected for a diffusion controlled process namely $8 \times 10^{6}$ $M^{-1}sec^{-1}$ Furthermore, the critical separation, $R_{o}$, between $Tb^{3+}$ (donor) and $En^{3+}$ (acceptor) was found to be about 13 A, These observations imply that the transfer process takes place either via complex multipolar interactions or via exchange interactions which are activation energy controlled.
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This project was supported by Owens-Illinois Incorporated, Corporate Laboratories, Toledo, Ohio.
Author Institution: Department of Chemistry, The University of Toledo
Author Institution: Department of Chemistry, The University of Toledo