Visible and near-UV radiation

Tests using hemicellulosic extracts from several different pulp stocks indicate that little if any discoloration is caused by exposure of these components to visible and near-UV radiation or even radiation at 254 nm (UV). In the continuing quest to understand the causes of discoloration in paper, these results support the contention that the tendency of hemicelluloses to lead to discoloration is primarily a thermally induced effect. 

Values are for nonresonant scattering of visible and near-uv radiation by atmospheric gases resonant Raman scattering approaches 10 ... 

Although pure paraffins are transparent to visible and near UV radiations penetrating the atmosphere, chromophores are nearly always... 

Optical Properties and Radiation Effects. Within the range of wavelengths measured (uv, visible, and near-ir radiation), Teflon PFA fluorocarbon film transmits slightly less energy than FEP film (29) (Table 6). In thin sections, the resin is colorless and transparent in thicker sections, it becomes translucent. It is highly transparent to it radiation uv absorption is low in thin sections. Weather-O-Meter tests indicate unlimited outdoor life. 

As shown in Table 25-2, there are two general types of transducers one type responds to photons, the other to heat. All photon detectors are based on the interaction of radiation with a reactive surface either to produce electrons (photoemission) or to promote electrons to energy states in which they can conduct electricity (photoconduction). Only UV, visible, and near-IR radiation possess enough energy to cause photoemission to occur thus, photoemissive detectors are limited to wavelengths shorter than about 2 p.m (2000 nm). Photoconductors can be used in the near-, mid-, and far-IR regions of the spectrum. 

Hg-Xe. This lamp is used to simulate the solar radiation as it is an intense ultraviolet (UV), visible and near-IR radiation source.The lamp contains... 

The polyphosphazene backbone is also transparent to radiation from the near infrared to 220 nm. That explains their stability to radiation in the visible and near-UV region and the interest in polyphosphazenes as optical and photonic materials. ... 

The N and K values are plotted over the visible and near UV spectrum in Figure 24.1. The plot is separated to show the detail near resonance at 7.043 x 10 rad/s and where the N becomes greater than zero at 9.8 x 10 rad/s. Between these frequencies, the N is zero and from Equation 24.26 the reflectivity will have the value of 1. Therefore, the high frequency limit of quartz is 7.043 x 10 rad/s, which is equivalent to 267 nm (UV). For very thin films (<267 nm), some radiation can penetrate, but it will be quickly absorbed because of the very large K in this region. For o) 9.8 x 10 rad/s, the electronic vibrations are no longer able to keep up with the oscillating E-field of the photons, thus there will little... 

The instrumentation used for UV space astronomy is, in most respects, similar to that used in ground-based astronomy. The differences have to do, primarily, with the following (1) UV radiation is not transmitted as efficiently by, or by as wide a variety of, transparent materials (used for windows, lenses, and other refractive optical elements) as are visible and near-infrared radiation and (2) reflective coatings for mirrors and reflection gratings are not as... 

PVF is transparent to radiation in the uv, visible, and near in regions, transmitting 90% of the radiation from 350 to 2,500 nm. Radiation between... 

Some polymeric materials become conductive when illuminated with light. For instance, poly(A -vinylcarbazole) is an insulator in the dark, but when exposed to UV radiation it becomes conductive. Addition of electron acceptors and sensitizing dyes allows the photoconductive response to be extended into the visible and near-IR (NIR) regions. In general, such photoconductivity is dependent on the material s ability to create free-charge carriers, electron holes, through absorption of light, and to move these carriers when a current is applied. 

Incandescence is the emission of radiation over the UV, visible and near-IR regions from a heated body. 

Amorphous polymers characteristically possess excellent optical properties. Unlike all the other commercially available fluoropolymers, which are semicrystalline, Teflon AF is quite clear and has optical transmission greater than 90% throughout most of the UV, visible, and near-IR spectrum. A spectrum of a 2.77-mm-thick slab of AF-1600 is shown in Figure 2.5. Note the absence of any absorption peak. Thin films of Teflon AF have UV transmission greater Ilian 95% at 200 mm and are unaffected by radiation from UV lasers. The refractive indexes of Teflon AF copolymers are shown in Figure 2.6 and decrease with increasing FDD content. These are the lowest refractive indexes of any polymer family. It should be noted that the abscissa could also be labeled as glass transition temperature, Tg, since Tg is a function of the FDD content of the AF copolymer. Abbe numbers are low 92 and 113 for AF-1600 and AF-2400. 

Transparent PVF films are essentially transparent to solar radiation in the near UV, visible, and near-infrared regions of the spectrum.95... 

The spectral characteristic of this light depends on the kind of the source the incandescent lamps are used primarily as sources of polychromatic visible light characterized by a continuous spectrum electrical discharge lamps produce band or line spectra in UV, visible and near-IR regions, whereas resonance lamps emit resonance radiation of atoms and their ions in the form of line spectra and can be used as sources of monochromatic light, eg Hg (184.9 and 253.7nm), Cd (228.8 and 643.8nm), Na (589.0nm), Zn (213.8, 330.0, 334.5, and 636.2nm), Kr (116.5 and 123.6nm), Xe (129.6 and 147.0nm) [1]. 

A semiconductor suitable for an efficient photo-oxidation reactions of environmental relevance should fulfil several requirements. Its bandgap should allow the use of solar radiation, ie the catalyst has to absorb in the visible or near-UV light region. The redox potentials of 0H7H20 and 02/02 couples should lie within this bandgap ( 0H./H20 = 2.8V [62], E°02/0.- = -0.16V [63]) in order to facilitate... 

Electromagnetic radiation in the visible and near-ir and uv regions of the spectrum, particularly with energies between approximately 33,000 and 4,000 cm (3,000-25,000 A, 4-0.5 eV) interacts with the eleetrons in solids (or liquids and gases). These interactions give rise to the processes of absorption and reflection qualitatively observed in minerals as the properties of color and luster. The quantitative measurement of such absorption and reflection processes forms the basis of eleetronic (optieal) absorption spectroscopy. The absorption and reflection phenomena arise from electronic excitation processes involving the valence electrons, excitation processes that may be of several kinds ... 

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