Depolarization rotational

Under the (fluid) conditions necessary to promote photoassociation, the excimer fluorescence is rotationally depolarized however, measurements of pyrene crystal fluorescence have confirmed81 the predicted direction of polarization along the major axis. 

Most interesting applications of intramolecular energy transfer between nonconjugated chromophores are found in the conformational studies of biomolecules like nucleic acids and proteins. The experiments on rotational depolarization of emission from intrinsic fluorescent groups on externally attached fluorescent probes, have resulted in a vast store of knowledge which has helped to enrich the subject of photobiology. 

Relaxation oscillator, 307 Resonance radiation, 99 Rotational depolarization, 120 Rotational relaxation time, 119 Russell-Saundets coupling, 21... 

Researches on theoretical topics have not been reported very extensively. A few papers are mentioned here and some others at appropriate points later in the article. Weber has re-examined the famous Perrin equation for quantifying the rotational depolarization of fluorescence. The arguments presented in the paper are applied to the temperature dependence of the local motions of tyrosine and tryptophan residues observed in proteins. 

Steady-state fluorescence anisotropy In low-viscosity solvents the rotational depolarization of low molecular weight compounds occurs on the picosecond timescale [124]. Since in this case the rotation is much faster than the fluorescence, the steady-state emission is unpolarised. If the rotational motion of the fluorophore is on the same timescale as the fluorescence, a steady state polarisation is observed. In the simplest case for a spherical rotor and a single-exponential fluorescence intensity decay (r), the measured anisotropy is given by... 

Kawski A (1993) Fluorescence anisotropy—theory and applications of rotational depolarization. CritRev Anal Chem 23(6) 459-529. doi 10.1080/10408349308051654... 

At this point, we should emphasize that depolarization occurs because of electronic mixing and rotation of the internuclear axis. In the very far wing this rotational depolarization will decrease since rotation of the nuclear axis becomes smaller as the trajectories become more and more curved. 

Fluorescence polarization is frequently expressed in terms of anisotropy (r) due to the comparatively simple equations describing rotational depolarization. The dependence of fluorescence anisotropy on molecular rotation can be described quantitatively with the well-known Perrin equation. 

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