Ultraviolet emitters

Celsius. The energy distribution of the radiation emitted by this surface is fairly close to that of a classical black body (i.e., a perfect emitter of radiation) at a temperature of 5,500°C, with much of the energy radiated in the visible portion of the electromagnetic spectrum. Energy is also emitted in the infrared, ultraviolet and x-ray portions of the spectrum (Figure 1). 

Possibilities exist for the involvement of halo-genated species such as CCI2F2 (CFC-12) or CCI3F (CFC-11) inasmuch as they can influence the column amounts of stratospheric O3 which is both a strong absorber of solar ultraviolet radiation and an absorber and emitter of infrared radiation. (Refer back to Fig. 7-11 for a survey of the chemical reactions that are involved.)... 

G. Spitzer, Multiphonon Lattice Absorption D. L. Slierwall and R F. Potter, Emittance Studies H- R- Philipp and H. Ehrenveich, Ultraviolet Optical Properties M. Cardona, Optical Absorption above the Fundamental Edge . J. Johnson, Absorption near the Fundamental Edge... 

The vacuum ultraviolet photolysis of formic acid yielded blue fluorescence, although the emitter was not identified [Style and Ward (953)]. 

Tissue also contains some endogenous species that exhibit fluorescence, such as aromatic amino acids present in proteins (phenylalanine, tyrosine, and tryptophan), pyridine nucleotide enzyme cofactors (e.g., oxidized nicotinamide adenine dinucleotide, NADH pyridoxal phosphate flavin adenine dinucleotide, FAD), and cross-links between the collagen and the elastin in extracellular matrix.100 These typically possess excitation maxima in the ultraviolet, short natural lifetimes, and low quantum yields (see Table 10.1 for examples), but their characteristics strongly depend on whether they are bound to proteins. Excitation of these molecules would elicit background emission that would contaminate the emission due to implanted sensors, resulting in baseline offsets or even major spectral shifts in extreme cases therefore, it is necessary to carefully select fluorophores for implants. It is also noteworthy that the lifetimes are fairly short, such that use of longer lifetime emitters in sensors would allow lifetime-resolved measurements to extract sensor emission from overriding tissue fluorescence. 

The wide band gap semiconductor ZnO has attracted much attention in recent years. This is stimulated by the development of transparent electronics, the growing need of emitters and detectors working in the ultraviolet range of the electromagnetic spectrum, and the progress in the realization of ferromagnetic semiconductors with Curie temperatures close to or above room temperature. ZnO is nowadays applied as transparent front contacts of solar cells competing with the commonly used material indium tin oxide (ITO). The low cost of ZnO as well as the radiation hardness make... 

Electrodes in fluorescent lamps (coated W or NS-W). Fluorescent lamps are low-pressure mercury discharge lamps which radiate in the UV region. The ultraviolet radiation is converted into light by means of a fluorescent layer (phosphor). Tungsten coils, coated with a mixture of Ca, Ba, and Sr compounds, are used as electrodes (emitter). 

X-ray sources, like ultraviolet and visible emitters, often produce both continuum and fine spectra both types are of importance in analysis. Continuum radiation is also called whhe radiation or hremsstrahfung. Brenisstrahlung means radiation fhat arises from retardation of particles such radiation is generally a spectral continuum. 

Different radioactive sources can initiate free-radical polymerizations of vinyl monomers. They can be emitters of gamma rays, beta rays, or alpha particles. Most useful are strong gamma emitters, like to or Sr. Electron beams from electrostatic accelerators are also efficient initiators. The products from irradiation by radioactive sources or by electron beams are similar to, but not identical to, the products of irradiation by ultraviolet light. Irradiation by ionizing radiation causes the excited monomer molecules to decompose into free radicals. Ionic species also form from initial electron... 

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