Polarization of fluorescent light

Polarization of fluorescent light from a uniaxially oriented rubber. J. Polymer Sci. 6,1975 (1968). 

As polarization arises from the mode of vibration of an atom or molecule, both bands and lines in luminescence spectra suffer polarization. Since polarization of fluorescent light is closely associated with the life time of the excited state, a lower limit for the life time of excited state of many organic compounds was obtained37 by consideration of the linear polarization of fluorescence in media of high and low viscosity by using Perrin s law of depolarization41, which connects polarization with the life time of the excited state and the relaxation time of molecular rotation. 

Here P is the degree of polarization of fluorescent light emitted at right angles to the direction of the incident light, tq is the lifetime of the excited state of the fluorescence, and Pq is an empirical constant. The rotational diffusion coefficient 0h is obtained from... 

A depolarization measurement consists of exciting a fluorescent sample with linearly polarized light and measuring the polarization of emitted light at right angles to the plane of excitation. The polarization of the emitted light is defined as... 

Fig. 2.5. The geometry adopted in calculating the degree of polarization V and the anisotropy of polarization of fluorescence 77 at excitation by linear polarized light beam directed along the a -axis with E z.

Let us consider the hyperfine depolarization effect caused by the presence of nuclear spin that is not oriented or aligned by light but acts as a randomly oriented flywheel to reduce the average polarization of fluorescence. The emission process can be effected by the presence of nuclear spin J, even if the hyperfine structure is unresolved by the detection apparatus. For this purpose one has to multiply each polarization moment fq in Eq. (5.34) by a coefficient g(K which is equal to [177, 402]... 

FP is an alternative readout principle for endopeptidase activity assays. FP or anisotropy measurements allow the detection of changes in the rotational correlation time of particles. These differences in the rotational correlation (or relaxation) time are related to different masses of particles. The experimental determination of steady-state fluorescence anisotropy requires the linear polarization of the light used for the excitation of the probe as well as linear polarization of the emitted fluorescence. Based on data of an appropriate experiment, the fluorescence anisotropy can be calculated as ... 

The degree of polarization of fluorescence after the absorption of polarized light can tell us whether the excitation has been transferred from one molecule to another. If the same chlorophyll molecules that absorbed polarized light later emit photons when they go back to the ground state, the... 

HPhe polarization of fluorescence technique employing dye-macromolecule x conjugates is a sensitive hydrodynamic method for studying the structure and interactions of proteins 19, 20, 41, 54, 65) and synthetic polypeptides 26, 30, 31, 49)- The relationship describing the dependence of polarization of fluorescence upon the Brownian rotational diffusion of the macromolecule was developed by Perrin 50) and extended by Weber 65) in the form of the equations (for excitation with natural light) ... 

This is the consequence of photoselective excitation of luminophores by polarized light, which selectively excites a population of molecules oriented with respect to the electrical vector of excitation. Emission also occurs with the light polarized along a fixed axis in the luminophore. The angle between these moments determines the maximal polarization of fluorescence. - Luminescence polarization is defined as follows ... 

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