UV spectral region

These devices have special function, namely to irradiate the liquid phase with light to induce a photoreaction or photoinduced reaction. Hence the characteristic feature is a transparent section within the reactor, often in the visible or commonly in the UV spectral region. The devices may have integrated photo energy sources or on-line analysis units. Otherwise, this is performed by external instruments. 

Anthraquinones are nearly perfect sensitizers for the one-electron oxidation of DNA. They absorb light in the near-UV spectral region (350 nm) where DNA is essentially transparent. This permits excitation of the quinone without the simultaneous absorption of light by DNA, which would confuse chemical and mechanistic analyses. Absorption of a photon by an anthraquinone molecule initially generates a singlet excited state however, intersystem crossing is rapid and a triplet state of the anthraquinone is normally formed within a few picoseconds of excitation, see Fig. 1 [11]. Application of the Weller equation indicates that both the singlet and the triplet excited states of anthraquinones are capable of the exothermic one-electron oxidation of any of the four DNA bases to form the anthraquinone radical anion (AQ ) and a base radical cation (B+ ). 

Some detectors for the visible and UV spectral regions can detect individual photons. These detectors are shot-noise limited. X-ray and gamma-ray spectroscopy also detects... 

Luminescence covers all emissions of light in the near IR, VIS and near UV spectral regions. The origin of the luminescence can be specified as photoluminescence , electroluminescence , chemiluminescence , or bioluminescence for example. These definitions depend on the mode of formation of the excited molecule which eventually emits the luminescence. 

Figure 1. Relative spectral responses of different broadband detectors in the UV spectral region. The dashed line corresponds to the CIE action spectrum. The numbers in the legend correspond to the weighted integral (Warm 2) of a standard solar spectrum (30° SZA, 330 DU).

Unlike NMR spectroscopy and vibrational spectroscopy, electronic spectroscopy involves interactions with electromagnetic waves in the near-infrared, visible, and ultraviolet (UV) spectral regions. While electronic spectroscopy... 

Absorption of a photon in the UV spectral region may lead to generation of electrophilic species by fast heterolytic bond cleavage at the photochemically excited state.10 Quinone methides are readily accessible through reactions of such photochemical excited states.11,12 This section outlines photochemical pathways for the generation of quinone methides. 

For practical proposes, it is important to know the nature of the excited state involved in any photoreaction. Some reactions occur in the singlet excited state while others take place in the triplet state manifold. The former are normally carried out by using direct irradiation and, therefore, the starting compound must absorb light in accessible UV-spectral regions. The latter reaction types usually require the use of a triplet sensitizer that absorbs the incident light and, after ISC, transfers its triplet energy to the diene reactant. 

Unsubstituted phenoxynaphthacenequinone is characterized by the absorption bands of the paraquinoid form in the UV spectral region and the ana form in the visible spectral range (Figure 7.8). 

The three components of the self-assembled structure have complementary properties so that new functions emerge from their assembly. Dendrimer 5 has a very high molar absorption coefficient in the UV spectral region because of 12 dimethoxybenzene and 16 naphthyl units, but it is unable to sensitize the emission of an Nd ion placed in its cyclam core. The [Ru(bpy)2(CN)2] complex can coordinate (by the cyanide ligands) and sensitize the emission of Nd ions. Self-assembly of the three species leads to a quite unusual Nd complex which exploits a dendrimer and an Ru complex as ligands. Such a system behaves as an antenna that can harvest UV to VIS light absorbed by both the... 

Cisplatin injection solutions (Img/mL), prepared in PVC bags and exposed to fluorescent radiation of approximately 1700 Lux, degraded substantially. After 24 hours, the TCAP content of cisplatin solutions reached 12% (34). The absorption spectrum of cisplatin, which has a UV maximum at 300 nm (35), overlaps the spectral power distributions of all UV-A and UV-B lamps. Therefore, cisplatin will rapidly degrade when exposed to radiation in the UV spectral region. As expected, cisplatin solutions have been shown to be more sensitive to fluorescent than to normal incandescent radiation, which is UV deficient. 

Figure 44, Absorption and (inset) uncorrected emission spectra in acetonitrile solution at 298 K of Cu.Sl" " (solid line) and of the analogous, previously studied copper) 1) [2]catenate Cu.25 (dashed line, Ref. [96]). The stronger absorption of the rotaxane in the UV spectral region is due to the presence of the aromatic-type stoppers.

Apart from the atomic and ion lines of the species present in a plasma source an emission spectrum has a continuum on which the emission lines are superimposed. This extends over the whole spectrum. It is due to the interactions between free electrons ( Bremsstrahlung ) and to the interaction of free and bound electrons ( recombination continuum ). The former is particularly important in the UV spectral region, whereas the latter is important at longer wavelengths. The spectral intensity distribution for the continuum radiation is given by ... 

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