Wavelength-dependent behavior

Vanderlinden, R, Boue, S., Direct Photolysis of Penta 1,3 Dienes Recognition of Wavelength dependent Behavior in Solution, J. Chem. Soc., Chem. Common. 1975, 932 933. 

Opaque nonmetals generally have high emissivities and can exhibit highly wavelength-dependent behavior [159]. Many nonmetals have behavior that deviates radically from that predicted by electromagnetic theory (Chap. 7), and available property measurements are less detailed than for metals. Again, recourse to use of measured property values is recommended. 

Polyethylene, the most-used commodity thermoplastic, also shows wavelength-dependent behavior in photodegradation. Heacock [135] proposed UV radiation of about A = 257 nm to result in the formation of unsaturated and oxygenated structures in polyethylene, while the longer wavelength UV-A radiation was believed to cause mainly crosslinking reactions. Results from a monochromatic exposure study of low-density and high-density polyethylene... 

Attractive for the use of QDs are their long lifetimes (typically 5 ns to hundreds of nanoseconds), compared to organic dyes, that are typically insensitive to the presence of oxygen. In conjunction with time-gated measurements, this provides the basis for enhanced sensitivity [69]. This property can be also favorable for time-resolved applications of FRET. The complicated size-, surface-, and wavelength-dependent, bi- or multi-exponential QD decay behavior (Fig. 2) can complicate... 

Figure 8 The time-dependent behavior of the hydrated electron obtained in the subpicosecond pulse radiolysis of neat water using 2-mm optical path sample cell, monitored at the wavelength of 780 nm.

Fig. 1. a) Probe wavelength-dependent transients for GFP. b) Pump-probe transients emphasizing the matching behavior of induced emission and near-infrared induced absorption, (c). Comparison of DTS (solid) and stationary emission (dashed). 

Halpern and Ware (97) have correlated wavelength-dependent lifetime measurements with those measured at various temperatures. If the amount of energy made available from optical excitation is assumed equivalent to a thermal excitation at higher temperatures, the lifetime results match quite well. This temperature dependence varies in some manner that is more complicated than simple Arrhenius behavior. 

Of special interest is the marked dependence of < >iSq for both 11-cis and all-trans molecules, on Aexc (176). As in the case of retinal (174,178), no quantitative rationalization of this wavelength dependence is available. However, as we shall subsequently see, the strikingly different photochemical behavior of the biopigments in this respect has provided the basis for a quantitative description of the primary photochemical event in rhodopsins. 

The photolysis of Mu2(CO)io is representative of the behavior of many bimetallic carbonyl compounds. In solution and in the gas phase strongly wavelength dependent photochemistry has been observed. At low energy, Mn-Mn bond homolysis predominates while at high energy CO-loss is observed. 

In contrast to the typical behavior of organic compounds discussed above, many photoreactions of transition metal complexes have wavelength-dependent quantum yields (7). Generally, these wavelength effects have been interpreted in terms of more than one reactive excited state of the photolyzed species. The photoreactivity of V(CO) L (L = amine), for example, has been interpreted in this manner with the previously mentioned model of substitutional photoreactivity proposed by Wrighton et al. (42, 49,73). Assuming ligand dissociation to be the only primary photochemical process (Section III-B-1), photolysis of W(C0)5L could produce three primary products ... 

The , values of various 1,2-diarylethylenes [301-305] are listed in Table lib. The StPs show rather small fluid media the effects of substitution and the position of the N atom, solvent polarity, and pH value were studied by Mazzucato and his group [129, 301, 302]. For 3-StP and its derivatives Of increases on increasing solvent polarity and acidity, whereas only small effects were found for 2- and 4-StP. Wavelength-dependent values indicate an anomalous emission behavior for 3-azastil-benes. Of values of 2- and 4-StP are an order of magnitude smaller than those of 3-StP. In EPA at — 196°C formation of nonfluorescing associates has been assumed [131]. 

Figure 9.9 shows the measured wavelength-dependence of ns for materials used in visible and infrared optics. We have included these as examples (and because their spectral behavior is studied most extensively) and not because of their common use in heat transfer in porous... 

A typical RTP factor (size 0 [1 m]) is shown in Fig. 18.56a. The thermal response of the silicon wafer is driven by radiation, with conduction and convection induced by radiative heating. The wafer s local radiative heating rate results from an interplay between (primarily) surface radiation effects and is determined by an imbalance between irradiation, emission, reflection, and, possibly, some transmission. Surfaces exhibit specular behavior, while the indirect heat sources (lamps) and associated windows have strongly wavelength-dependent absorption characteristics [217],... 

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