Forward angle ratio

A technique for sizing monodisperse particles of unknown refractive index uses the observation that the intensity of the forward scattering lobe is mainly due to Fraunhofer diffraction and is thus independent of the refractive index of the particle. Hodkinson (1966) computed a family of curves for the ratio of intensity viewed at two different angles. This relationship is shown in Fig. 17.10. If forward angles as small as 5° can be measured, this procedure should be accurate in measuring particle sizes of a = 1 to a = 18. 

To better quantify influences of resonant wavelengths on emission characteristics, four parameters are defined the outcoupling efficiency, which is the ratio of the outcoupled emission to internally generated emission the forward enhancement ratio, which is the ratio between the normal-direction luminance of a cavity device to that of an optimized conventional bottom-emitting OLED the color shift, which is defined as [variance of w (0) + variance of w (0)j and measures variation of colors over angles and the Lambertian offset, which is defined as E 1(9)/1(0°) - cos 01 and measures the difference between the emission pattern of a device and the ideal Lambertian distribution (where J(0) is spectrally integrated I(Q,X)). Values of these parameters are obtained using both the simulated data and the measured EL characteristics. 

This corresponds to (f + d" ) lv(0), except that for the present pourposes we took into account the dispersionof f by an additional factor 1.4. N is the number of resonant atoms which form a definite structure, e.g. as metal binding sites a macromolecule. The ratio of resonant zero angle scattering to fluorescence Op in forward direction is... 

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