PHOTOSELECTION EFFECTS IN OPTICAL ACTIVITY STUDIES
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Date
1978
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Publisher
Ohio State University
Abstract
Studying the optical activity in oriented molecular systems may yield additional spectroscopic information which is otherwise lost in the process of averaging the optical activity of an isotropic distribution of molecules. We obtain oriented samples of electronically excited molecules by illuminating a frozen sample of randomly distributed molecules with unpolarized light or with light of a known mode of polarization. The optical activity of the photoselected molecules may be studied by the circular polarization in their luminescence $(CPL),^{1}$ and the ground state optical activity may be evaluated through the fluorescence detected circular dichroism (FDCD).$^{2}$ A theoretical evaluation has revealed that such measurements yield the optical activity of the molecule for light propagating along discrete directions in the molecular framework. Moreover, upon photoselection with circularly polarised light, even achiral molecules may exhibit optical activity in their fluore $scence^{3}$ The effect of photoselection on CPL and FDCD measurements was demonstrated in the following cases: D-camphor and D-camphor quinone in glycerol solutions, (-) hexahelicene in a plastic glass, and auramine-0 tightly bound to the enzyme alcohol dehydrogenase.
Description
$^{1}$ I. Z. Steinberg and B. Ehrenberg, J. chem. Phys. 61, 3382 (1974). $^{2}$ B. Ehrenberg and I. Z. Steinberg, J. Am. Chem. Phys. Soc. 98, 1293 (1976). I. Tinoco, B, Ehrenberg and I. Z. Steinberg, J. Chem. Phys. 66, 916, (1977) $^{3}$ B. Ehrenberg and I. Z, Steinberg, Chem, Phys. Lett. 49, 295 (1977). Present address of B. Ehrenberg: Department of Applied Physics, Cornell University, Ithaca, New York, 14853.""
Author Institution: Department of Chemical Physics,, Weizmann Institute of Science,
Author Institution: Department of Chemical Physics,, Weizmann Institute of Science,