Radiation promoters

Shorter-wavelength radiation promotes transitions between electronic orbitals in atoms and molecules. Valence electrons are excited in the near-uv or visible. At higher energies, in the vacuum uv (vuv), inner-shell transitions begin to occur. Both regions are important to laboratory spectroscopy, but strong absorption by make the vuv unsuitable for atmospheric monitoring. Electronic transitions in molecules are accompanied by stmcture... 

Electronic absorption spectra are produced when electromagnetic radiation promotes the ions from their ground state to excited states. For the lanthanides the most common of such transitions involve excited states which are either components of the ground term or else belong to excited terms which arise from the same 4f" configuration as the ground term. In either case the transitions therefore involve only a redistribution of electrons within the 4f orbitals (i.e. f—>f transitions) and so are orbitally forbidden just like d—>d transitions. In the case of the latter the rule is partially relaxed by a mechanism which depends on the effect of the crystal field in distorting the symmetry of the metal ion. However, it has already been pointed out that crystal field effects are very much smaller in the case of ions and they... 

Ionizing radiation promotes the alkylation in the following reaction250 ... 

Absorption of visible or ultraviolet radiation promotes electrons to higher-energy orbitals in formaldehyde. Infrared and microwave radiation are not energetic enough to induce electronic transitions, but they can change the vibrational or rotational motion of the molecule. 

Infrared radiation promotes electrons from the valence band of silicon to the conduction band. Semiconductors that are used as infrared detectors have smaller band gaps than silicon... 

There has recently been interest in the photoelectrolysis of water (Section 12.4). In this process a large part of the energy necessary for electrolysis is provided photochemically by solar radiation, promoting the reactions by exciting the valence electrons in semiconductor electrodes. This electronic energy is then transferred to the water molecules, helping to break the O-H bonds. Efficiencies achieved so far are still not high, and it is not clear at present what future this will have. 

Radiation Promotion of Bowden et al. Cyclosporin increases Yabu Test system Usually requires... 

As a whole, these investigations provided valuable criteria to differentiate between the contributions ofthe various labeling mechanisms, and to determine their relative weight in the formation of the tritiated products. The currently accepted view (cf. Evans, 1966) is that the Wilzbach labeling method is essentially based on radiation-promoted processes, which largely predominate over the reactions of the HeT+ ions, as demonstrated by the fact that several T atoms are incorporated following each /8-decay. Under typical preparative conditions, the... 

Cross-linking of ETFE improves its high-temperature properties, such as cut-through by a hot soldering iron, and increases the continuous service temperature from 150°C (302°F) to 200°C (392°F) [36]. Further improvement is achieved by the use of prorads (radiation promoters) such as triallyl cyanurate (TAC) or triallyl iso-cyanurate (TAIC) in amounts up to 10% by weight [25]. 

Prorad Radiation promoter, a compound promoting or enhancing the cross-linking reaction by high-energy (ionizing) radiation. 

Each new chemical added to our environment potentially creates a vast number of new chemical mixtures with unknown health consequences. The number of compounds is multiplied by the chemical reactions of newly released compounds with existing released compounds as well as with naturally occurring species to create yet more toxic molecules. Continual exposure to electromagnetic radiation promotes further chemical reactivity... 

Figure 5 Formation of oxidizing radicals at the solid-liquid interface of TiO and water. Radiation promotes a separation of charge In the catalyst. H2O, ( H, and O2, adsorbed at the surface are converted to radicals by electrons and holes which migrate to the Interface. Oxidative degradation Is greatly enhanced (see also Fig. 4).

A.T. Davidson, van der Heijden (2000). Exposure of natural Antarctic marine plankton assemblages to ambient UV radiation promotes bacterioplankton growth and the microbial loop. Aquat. Microb. EcoL, 21, 257-264. 

Nuclear waste (Section II.A.2) presents even more serious problems than does chemical waste. No method of elimination is possible radioactive material must be sequestered from the environment until it decays, which for some common by-products of nuclear reactor operation will take thousands of years. Continual exposure to radiation promotes deterioration of materials, so nuclear wastes held in aboveground storage or in subsurface tanks must frequently be transferred to new containers. Burial of such wastes has frequently been discussed as a long-term solution to the problem of their disposal, but finding geological formations sufficiently stable and remote from aquifers into which the wastes might migrate has proven to be very difficult. At present, ahention is fo-... 

Does Ionising Radiation Promote Pneumoconiotic Fibrosis ... 

Complete cyanide recoveries are typically attained for the most important metal-cyanide complexes found in environmental samples. Detection limits below 0.05 pg/1 have been reported. The main drawback of this system is that the UV radiation promotes thiocyanate decomposition, what leads to sulfide and cyanide formation. To overcome this problem, it is recommended to use borosilicate glass instead of a quartz reactor, which cuts off radiation below 300 nm. 

Molecular fluorescence is caused by irradiation of molecules in solution or in the gas phase. As shown in Figure 6-24a, absorption of radiation promotes the molecules into any of the several vibrational levels associated with the two excited electronic levels. The lifetimes of these excited vibrational states are, however, only on the order of 10" s, which is much smaller than the lifetimes of the excited electronic states (10 s). Therefore, on the average, vibrational relaxation occurs before electronic relaxation. As a consequence, the energy of the emitted radiation is smaller than that of the absorbed by an amount equal to the vibrational excitation energy. For example, for the absorption labeled 3 in Figure 6-24a, the absorbed energy is equal to ( 2 0 + Co), whereas the energy of... 

The model postulates that diffuse cloud grains are composed of cores of silicate (some large, 2000 A and some small 100 A) each with a mantle of amorphous carbon (typical thickness 50 A). Freshly deposited amorphous carbon contains much sp bonded carbon, i.e. is diamond-like this is the metastable form. Exposure to UV radiation promotes the conversion to the more stable graphite-like form (sp bonding predominates). In both types of amorphous carbon, however, no long range order exists. The time... 

Much of environmental chemistry and water chemistry are concerned with electrons in atoms. In the atmosphere, the absorption of electromagnetic radiation, primarily ultraviolet radiation, promotes electrons to higher energy levels, forming reactive excited species and reactive free radicals with unpaired electrons. These phenomena can result in photochemical reactions such as the formation of stratospheric ozone, which is an essential filter for solar ultraviolet radiation. Atomic absorption and emission methods of elemental analysis, important in the study of pollutants, involve transitions of electrons between energy levels. 

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