Emission studies

Nelson et al. [34] determined from void shapes that the ratio 7100/7110 was 1.2, 0.98 and 1.14 for copper at 600°C, aluminum at 550°C, and molybdenum at 2000°C, respectively, and 1.03 for 7100/7111 for aluminum at 450°C. Metal tips in field emission studies (see Section VIII-2C) tend to take on an equilibrium faceting into shapes agreeing fairly well with calculations [133]. 

Surface heterogeneity may be inferred from emission studies such as those studies by de Schrijver and co-workers on P and on R adsorbed on clay minerals [197,198]. In the case of adsorbed pyrene and its derivatives, there is considerable evidence for surface mobility (on clays, metal oxides, sulfides), as from the work of Thomas [199], de Mayo and co-workers [200], Singer [201] and Stahlberg et al. [202]. There has also been evidence for ground-state bimolecular association of adsorbed pyrene [66,203]. The sensitivity of pyrene to the polarity of its environment allows its use as a probe of surface polarity [204,205]. Pyrene or ofter emitters may be used as probes to study the structure of an adsorbate film, as in the case of Triton X-100 on silica [206], sodium dodecyl sulfate at the alumina surface [207] and hexadecyltrimethylammonium chloride adsorbed onto silver electrodes from water and dimethylformamide [208]. In all cases progressive structural changes were concluded to occur with increasing surfactant adsorption. 

Leone S R 1989 Time-resolved FTIR emission studies of molecular photofragmentation Accounts Chem. Res. 22 139-44... 

Msphalt Hot-Mix Emission Study, Research Report RR-75-1, The Asphalt Institute, CoUege Park, Md., 1975. 

The total consumption type of burner consists of three concentric tubes as shown in Fig. 21.5. The sample solution is carried by a fine capillary tube A directly into the flame. The fuel gas and the oxidant gas are carried along separate tubes so that they only mix at the tip of the burner. Since all the liquid sample which is aspirated by the capillary tube reaches the flame, it would appear that this type of burner should be more efficient that the pre-mix type of burner. However, the total consumption burner gives a flame of relatively short path length, and hence such burners are predominantly used for flame emission studies. This type of burner has the advantages that (1) it is simple to manufacture, (2) it allows a totally representative sample to reach the flame, and (3) it is free from explosion hazards arising from unbumt gas mixtures. Its disadvantages are that (1) the aspiration rate varies with different solvents, and (2) there is a tendency for incrustations to form at the tip of the burner which can lead to variations in the signal recorded. 

The synthesis and characterization of ci.v-[Ir(diimine)(hdpa)C12]C1, diimine = bpy, phen, hdpa = 2,2 -dipyridylamine, is reported.135 Emission studies suggest that it is the Ir(diimine)... 

The emissions study identified and provided computations of the concentration, exposure, and dosage patterns for the following. 

Naik LR, Naik AB, Pal H (2009) Steady-state and time-resolved emission studies of thioflavin-T. J Photochem Photobiol A Chem 204 161-167... 

Those organometallic thexi states which have been detected have involved compounds where the quantum yield for photodissociation is very low. Time-resolved uv-visible absorption and emission studies have been made on W(CO)5L and W(CO)4L species (L = acetylpyridine, L = o-phenanthroline) (54), but, as in the case of intermediates, these studies provided lifetimes but no structural information. 

H. Schade, Irradiation-Induced Metastable Effects L. Ley, Photoelectron Emission Studies... 

Similar results have been presented by Miller and co-workers, who capped the ends of oligo(dihexylfluorene)s and poly(dihexylfluorene)s with Frechet-type dendrons (Figure 7.17C) [73], Annealing experiments coupled with emission studies revealed that G-3 and G-4 dendrons were effective at preventing excimer formation, even when the poly(fluorene) spacer was 50-80 repeat units long. 

Both the Na and K intensities in the K-feldspar profile of Figure 4 are stable with depth indicating a previously documented lack of alkali mobility in the surface layers of feldspars at low temperature (7). In contrast, K increases and Na decreases with depth beneath the obsidian surface demonstrating substantial elemental mobility. The K loss near the surface corresponds to a concentration increase measured in aqueous solution. Sodium profiles in obsidian should exhibit even greater near-surface losses relative to K based on profiles measured by HF leaching (3) and sputter-induced optical emission studies (6). 

FTIR Emission Studies, Time Resolved, of Photochemical Reactions... 

For emission studies, stilbene and naphthalene anion radicals have been successfully employed as the weak pi acid in this procedure.2... 

Most solution-electrochemiluminescence emission studies have been made by applying 3-10 V across platinum electrodes, frequently... 

In one study of the effects of additives,9 it was found that on electrochemical oxidation of rubrene, emission was seen in dimethylforma-mide, but not in acetonitrile. When water, n-butylamine, triethylamine, or dimethylformamide was added to the rubrene solution in acetonitrile, emission could be detected on simply generating the rubrene cation.9 This seems to imply that this emission involves some donor or donor function present in all but the uncontaminated acetonitrile system. The solvent is not the only source of impurity. Rubrene, which has been most extensively employed for these emission studies, is usually found in an impure condition. Because of its relative insolubility and its tendency to undergo reaction when subjected to certain purification procedures, and because the impurities are electroinactive and have relatively weak ultraviolet absorptions, their presence has apparently been overlooked, They became evident, however, when quantitative spectroscopic work was attempted.70 It was found, for example, that the molar extinction coefficient of rubrene in benzene at 528 mjj. rose from 11,344 in an apparently pure commercial sample to 11,980 (> 5% increase) after repeated further recrystallizations. In addition, weak absorption bands at 287 and 367 m, previously present in rubrene spectra, disappeared. 

Besides these laboratory experiments there are several emission studies on controlled tyre co-combustion in large-scale industrial facilities, including cement and lime kilns, utility boilers, and pulp and paper mills (Ohio Air Quality Development Authority 1991 EPRI 1991 EPA... 

The term in Eq. (49) which describes radiative decay is relatively small under conditions where stimulated emission does not occur. Thus, only when all other contributions to the over-all decay are accurately determined will this term be accessible. At present only time-resolved atomic emission studies provide the required precision.11 The mean radiative lifetime has been obtained by observing the variation in the first-order decay coefficient for this emission as a function of inert gas pressure (Fig. 11). The slope of the graph so obtained yields the diffusion coefficient, while the intercept represents the sum of... 

Early field ion emission studies of gas-surface interactions use field ionization mass spectrometry. Gas molecules are supplied continuously to the tip surface by a polarization force and by the hopping motion of the molecules on the tip surface and along the tip shank. These molecules are subsequently field ionized. The role of the emitter surface in chemical reactions is not transparent and has not been investigated in detail. Only in recent pulsed-laser stimulated field desorption studies with atom-probes are these questions addressed in detail. We now discuss briefly a preliminary study of reaction intermediates in NH3 formation in pulsed-laser stimulated field desorption of co-adsorbed hydrogen and nitrogen,... 

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