Spectra, light

Yet another approach to sensitizing PCs to a broader light spectrum is to use composite materials with a heterojunction (Fig. 6) between a narrow band gap and wide band gap semiconductors. A particular... 

To optimize the conversion efficiency, physical focusing conditions need to be optimized. With reference to the SG spectrum shown in Fig. 5.8, for fixed incident laser power and fixed focal length of the lens, the location of the focus point within the 7.5 cm long barium fluoride crystal was found to determine the extent of the white light spectrum. With the focus located f cm inside the crystal, the flattest possible spectrum of white light was obtained (as shown in Fig. 5.8), and the highest conversion efficiency was also achieved. 

A clever adaptation of a special kind of fluorescence where the energy source is a chemical reaction is called chemiluminescence. The common firefly uses such a reaction to generate light in the green-yellow end of the visible light spectrum. The reaction involves an... 

Selecting an approach If available, a CO-Oximeter, an instrument used to test human blood by measuring its UV-Visible light spectrum, would be ideal. If unavailable, a standard UV-Vis will be used. 

When the frequency of a laser falls fully into an absorption band, multiple phonon processes start to appear. Leite et al 2° ) observed /7 h order ( = 1, 2. 9) Raman scattering in CdS under conditions of resonance between the laser frequency and the band gap or the associated exciton states. The scattered light spectrum shows a mixture of fluorescent emission and Raman scattering. Klein and Porto 207) associated the multiphonon resonance Raman effect with the fluorescent emission spectrum, and suggested a possible theoretical approach to this effect. 

For a 1 the scattered light spectrum is gaussian with a width determined by the electron temperature, because it is due to the incoherent sum of Thomson scattering from individual, thermally moving electrons. The intensity and spectral linewidth of scattered light therefore yield electron density and temperature. 

Chitosan films are also transparent in the UV and visible regions of the light spectrum and thus have little effect on most optical detection methods. Also, chitosan s amine groups are more reactive in aqueous environments compared to other polyamines because of the low pKa value possessed by the primary amine (6.3 for chitosan vs. 10.5 for polylysine). Finally, other advantages of chitosan are that it is safe, abundant and inexpensive. 

Another direction of investigation is to extend the nanotube array architecture to other metal oxides, most noticeably a-Fc203 and mixed FeTi oxides, to develop materials capable of efficiently responding to the visible light spectrum, while maintaining the outstanding charge transport properties demonstrated by the HO2 nanotube arrays. 

Physical Properties Density average and standard deviation Size average and standard deviation Fluorescence Fluorescence excitation spectrum Scattered light spectrum Absorption spectrum (from microwave to UV) Raman spectrum Electrical conductivity, impedance Acoustic properties... 

Still another method used to produce PV cells is provided by thin-film technologies. Thin films are made by depositing semiconductor materials on a solid substrate such as glass or metal sheet. Among the wide variety of thin-film materials under development are amorphous silicon, polycrystalline silicon, copper indium diselenide, and cadmium telluride. Additionally, development of multijunction thin-film PV cells is being explored. These cells use multiple layers of thin-film silicon alloys or other semiconductors tailored to respond to specific portions of the light spectrum. 

Silver halides are naturally sensitive to ultraviolet and blue light only. That it is possible to photograph objects of all colours is the consequence of the discovery, made in 1873, of the means of extending the sensitivity of silver halides into regions of the visible light spectrum beyond the blue. This was achieved by the addition of a dye in a small amount to a silver halide emulsion which was thereby rendered sensitive to the light absorbed by the dye (1873CB1302). 

Figure 7.13 Shape of the pump flash light spectrum and of the Q-switched laser light, t, time I, light intensity...

Color sensitizers are dyes added to silver halide emulsions to broaden their response to various wavelengths. Unsensitized emulsions are most responsive in the blue region of the spectrum and thus do not correctly represent the light spectrum striking them. Widely used sensitizers include the cyanine dyes, the merocyanines. the benzooxazoles, and the hcn/n11iki/oIl1 s Cryplocyaniiie sensitizes the extreme red and infrared. 

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