Ultraviolet, Visible, and Near-infrared Radiation

Mercury-xenon lamp (Arc) An intense source of ultraviolet, visible, and near infrared radiation produced by an electrical discharge in a mixture of mercury vapor and xenon under high pressure. 

Instruments for measuring the absorption of ultraviolet. visible, and near-infrared radiation are intide up ol one or more (I) sources, (2) wavelength selectors, (3) sample containers. (4) radiation transducers, and (.5) signal processors and readout devices. The design and peifoi mance of components (2). f4). and (5) were described in considerable tletail in Oiapier 7 and thus arc not discussed further here. We will, however, consider briefly the characteristics of sources and sample containers for the region of l9l) to nm. 

Energy provided by ultraviolet, visible and near infrared radiation. 

Ultraviolet, visible, and near-infrared radiation from lamps and lasers in the laboratory can produce a number of hazards. Medium-pressure Hanovia 450 Hg lamps are commonly used for ultraviolet irradiation in photochemical experiments. Powerful arc lamps can cause eye damage and blindness within seconds. Some compounds, for example, chlorine dioxide, are explosively photosensitive. 

Photochemistry is the branch of chemistry that deals with the causes and courses of chemical deactivation processes of electronically excited particles, usually with the participation of ultraviolet, visible, or near-infrared radiation [1]. The photochemist is interested in both the modes of excited-state formation processes (direct photoexcitation, energy transfer, etc.) and the deactivation pathways of excited atoms, molecules, and ions. 

Luminescence can be defined as the emission of light (as in the broad sense of ultraviolet, visible, or near-infrared radiation) by electronic excited states of atoms or molecules. Luminescence is an important phenomenon that is useful for monitoring excited-state behavior,183 as well as for utilitarian applications (e.g., laser, display, sensors).184 Since dendrimers are complex multifunctional constructs possessing well-defined chemical tree-like structures, a high degree-of-order, and capable of containing selected chemical units within predetermined sites in their structure, their incorporation into luminescence science can lead to systems capable of performing very... 

A. Fix, T. Schroder, R. Wallenstein New sources of powerful tunable laser radiation in the ultraviolet, visible and near infrared. Laser und Optoelektronik 23, 106 (1991)... 

The multiplex advantage is important enough so that nearly all infrared spectrometers are now of the Fourier transform type Fourier transform instruments are much less common for the ultraviolet, visible, and near-infrared regions, however, because signal-to-noise limitations for spectral measurements with these types of radiation are seldom a result of detector noise but instead are due to shot noise and flicker noise associated with the source. In contrast to detector noise, the magnitudes of both shot and flicker noise increase as the radiant power of the signal increases. Furthermore, the total noise for all of the resolution elements in a Fourier transform measurement tends to be averaeed... 

A. Fix, T. Schroder, and R. Wallenstein, New Sources of Powerful Tunable Laser Radiation in the Ultraviolet, Visible and Near Infrared , Laser und Op-toelektronik 23, 1991 (1991). 

Grenfell, T.C., S.G. Warren, and P.C. Mullen. 1994. Reflection of solar radiation by the Antarctic snow surface at ultraviolet, visible, and near-infrared wavelengths. Journal of Geophysical Research 99(D9) 18-669-18-684. 

PVF is transparent to radiation in the ultraviolet, visible, and near infrared light regions, transmitting 90% of the radiation from 350 to 2500 nm.PVF becomes embrittled upon exposure to electron-beam radiation of 1000 Mrad but resists breakdown at lower doses. While FIFE is degraded at 0.2 Mrad, PVF retains its strength at 32 Mrad. 

It may be helpful to explain the use of the terms rare earths and lanthanides throughout the text. By convenience, the term lanthanides refers to the elements La (Z = 57) to Lu (Z = 71). The term rare earths is commonly used for the lanthanides with inclusion of the elements Y (Z = 39) and Sc (Z = 21). Although one speaks often about rare-earth spectroscopy, the term lanthanide spectroscopy is preferable. The main objects of study in lanthanide spectroscopy are the trivalent lanthanide ions from Ce (4f ) to Yb3+ (4f ), since these ions have unpaired f electrons and can interact with ultraviolet, visible or near-infrared radiation. Divalent ions like Eu " " have gained less interest and will not be discussed here. The trivalent lanthanide ions La " (4f ) and Lu (4f ) are not spectroscopically active, because of an empty or filled 4f shell. The same is true for and Sc. Yttrium, lanthanum and to a lesser extent lutetium compounds are used as transparent host crystals in which other trivalent lanthanide ions can be doped. The trivalent lanthanide ions can readily substitute for Y, La " and Lu. Expressions like point group of the rare-earth site and the crystal field in rare-earth compounds are thus meaningful. 

Normal glass will only transmit radiation between about 350 nm and 3 /rm and, as a result, its use is restricted to the visible and near infrared regions of the spectrum. Materials suitable for the ultraviolet region include quartz and fused silica (Figure 2.28). The choice of materials for use in the infrared region presents some problems and most are alkali metal halides or alkaline earth metal halides, which are soft and susceptible to attack by water, e.g. rock salt and potassium bromide. Samples are often dissolved in suitable organic solvents, e.g. carbon tetrachloride or carbon disulphide, but when this is not possible or convenient, a mixture of the solid sample with potassium bromide is prepared and pressed into a disc-shaped pellet which is placed in the light path. 

Measurements of the gaseous sulfur dioxide released were obtained with the Total Ozone Mapping Spectrometer (TOMS Krueger, 1983) and with the Solar Backscatter Ultraviolet Spectrometer (SBUV Heath et d., 1983), both carried on the Nimbus 7 satellite. Three instruments on board the Solar Mesosphere Explorer (SME) also revealed features of the cloud the Infrared Radiometer measured the thermal emission from the aerosols, while the Visible and Near Infrared Spectrometers measured the backscat-tered solar radiation. The three instruments are limbscanning and view the atmosphere along the track of the sunsynchronous polar orbit (Barth et d., 1983 Thomas et d., 1983). Ground based and airborne spectro-photometric measurements of sulfur dioxide have also been carried out (Evans and Kerr, 1983). 

Laser Ocular Biology. The biological effects of laser radiation on the eyes vary with the laser wavelength, pulse duration, and intensity. The cornea and lens focuses visible and near-infrared laser radiation onto the retina where the concentrated energy directly impacts the photoreceptor cells and supporting tissue. The cornea and lens absorb ultraviolet and mid-to-far-infrared laser radiation. Alteration can occur in these tissues, but the retina will be spared. 

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