Ultraviolet radiation, sources

Ions can be produced more efficiently by ultraviolet irradiation than by bombardment with electrons. The sample and carrier gas are passed in front of an ultraviolet radiation source (10.2 ev), where the sample components are ionized, but not the major components of air such as Nj, Oj, CO HjO, CO, and Ar. 

Marangos JP, Shen N, Al HME (1990) Broadly tunable vacuum-ultraviolet radiation source employing resonant enhanced sum-frequency mixing in krypton. J Opt Soc Am B 7 1254-1259... 

From a commercial standpoint, ultraviolet radiation initiated cross-linking appears to have certain distinct attractions. Ultraviolet radiation sources are... 

Another factor in oxidative degradation is ultraviolet radiation, of which sunlight is a rich source. The oxidation of parylene appears to be enhanced by ultraviolet radiation. 02one may play a mechanistic role in the ambient temperature exposure of parylenes to ultraviolet radiation in the presence of oxygen. For the best physical endurance, exposure of the parylenes to ultraviolet light must be minimised. 

Ultraviolet light sources are based on the mercury vapor arc. The mercury is enclosed ia a quart2 tube and a potential is appHed to electrodes at either end of the tube. The electrodes can be of iron, tungsten, or other metals and the pressure ia a mercury vapor lamp may range from less than 0.1 to >1 MPa (<1 to >10 atm). As the mercury pressure and lamp operating temperatures are iacreased, the radiation becomes more iatense and the width of the emission lines iacreases (17). 

Nitro-substituted indolino spiroben2opyrans or indolino spironaphthopyrans are photochromic when dissolved in organic solvents or polymer matrices (27). Absorption of uv radiation results in the colorless spiro compound [1498-88-0], C22H2gN202, being transformed into the colored, ring-opened species. This colored species is often called a photomerocyanine because of its stmctural similarity to the merocyanine dyes (see Cyanine dyes). Removal of the ultraviolet light source results in thermal reversion to the spiro compound. 

Ultraviolet radiation in the region between 0.2 fi to 0.3 has germicidal properties. The peak germicidal wavelength is around 0.26 fi. This short UV is attenuated in air and, hence, the source must be very near the medium to be treated. The medium must be very thin as the UV will be attenuated in the medium as well. 

One of the most direct methods is photoelectron spectroscopy (PES), an adaptation of the photoelectric effect (Section 1.2). A photoelectron spectrometer (see illustration below) contains a source of high-frequency, short-wavelength radiation. Ultraviolet radiation is used most often for molecules, but x-rays are used to explore orbitals buried deeply inside solids. Photons in both frequency ranges have so much energy that they can eject electrons from the molecular orbitals they occupy. 

Visible and ultraviolet absorption spectra are measured in an absorption spectrometer. The source gives out intense visible light or ultraviolet radiation. The wavelengths can be selected with a glass prism for visible light and with a quartz prism or a diffraction grating for ultraviolet radiation (which is absorbed by glass). A typical absorption spectrum, that of... 

Radiation processing of polymers was introduced after World War II with the development of the nuclear reactor. In the current years, various radiation sources, e.g.. X-rays (soft and hard), gamma (7) and ultraviolet (UV) rays and electron beam (EB) are being widely used. 

R. Phillips, Sources and Applications of Ultraviolet Radiation, Academic Press, London, 1983. 

The thermal plasma is a source of high energy density with temperature of a few thousand degrees and high ultraviolet radiation. These result in fast reaction rates, high throughput in smaller reactors, heat generation independent of the chemical composition, avoidance of dioxins and furans... 

The usual sources of ultraviolet radiation are hydrogen or deuterium discharge lamps (the latter usually being preferred) or the mercury vapour lamp. All ultraviolet sources must be fitted with quartz or silica glass windows and none of the lamps named emits any significant amounts of radiation above 400 nm. 

A fluorimeter must have a source of ultraviolet radiation BECAUSE... 

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