Light Scattering Losses

Powders give statistically mixed phases and, possibly, spatially unseparated reduction and oxidation sites, as well as poor space charge layers for carrier separation. This leads to high rates of bulk and surface recombination, as well as solution species back reactions. Light scattering losses add a further decrease in... 

Proper definition of quantum yields (cp) requires the cai eful assessment of photons absorbed by the photocatalyst. Methods based on chemical actinometry ai e limited as they provide only the total rate of photons entering the reactor and do not account for various light scattering losses. The use of physical methods involving spec-trophotoradiometers and collimators (Salaices et al., 2001), as described in chapter IV, enables macroscopic energy balances, the proper assessment of irradiation energy absorbed by the photocatalyst and, consequently, an adequate definition of quantum efficiencies. 

Bulk Optical Absorption of Phthalocyanine Particles. The visible and near infrared optical absorption of the phthalocyanine pigments was measured on a Cary 17 spectrophotometer using the technique described in Reference 8. A thin film of phthalocyanine dispersed in the polymer was coated onto 3 mil Mylar substrate using wirewound rods. The dry films were index matched by overcoating with a thick film of polyvinyl alcohol. The differential absorption between two films with different thicknesses were recorded to minimize reflection and light scattering losses. The solution absorption spectra of some pigments were also measured in a-chloronapthalene. 

Light Scattering Loss of Zero-Birefringence Copolymer. Table II shows the scattering parameters of zero-birefringence poly(MMA-co-BzMA) and those of the homopolymer glasses. The Vy and Hy intensities of all samples had no angular... 

Light Scattering Loss of Zero-Birefringence PMMA with Dopant Molecules. 

Figure 2.9 Flowchart of empirical calculation of isotropic light scattering losses in amorphous polymers.

By combining the above relationships, the isothermal compressibility of polymers at Til can be calculated from the intrinsic molecular volume Vj, . However, the value of P at is necessary to estimate the light scattering loss in the glassy state, p increases linearly with T from to Tjj. It is interesting that the values of (1/ at between and Tn for many amorphous polymers are... 

Tanio, N. and Koike, Y, (1997) Estimate of light scattering loss of amorphous polymer glass from its molecular structure. Jpn. J. Appl. Phys., 36 (1-2),... 

Here, Ag is the wavelength of light in vacuum, n is the refractive index, k is the Boltzmann constant, T is the absolute temperature, is the isothermal compress-ibihty, N is the number of scattering units per unit volume, and (5 ) is the mean square of the anisotropic parameter of polarizability per scattering unit. Finally, from the definition of the turbidity r in Equation A8, the light scattering loss (dB/km) is related to the turbidity r (cm" ) by... 

Years later, I would find myself researching the fundamental reasons for light scattering loss - the prime reason why fibers could not be made transparent. While I remained a member of the polymer chemistry laboratory, on my own I entered the worlds of physics and optics as I studied subjects such as light scattering theory and polarization. I would continue to learn in the academic field of photonic polymers for the next 20 years, but my fundamental research method was the one that I learned at that time from Professor Otsuka. 

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