Shoulder case study

Based on previous studies [15, 22-25], the band at 1941 cm-i is assigned to Co2+(NO), and the pair of bands at 1894 and 1815 cm-i, to Co2+(NO)2- The shoulders at 1874 and 1799 cm may be due to a second dinitrosyl species. While little is known about the location and coordination of the Co 2+ in ZSM-5, it is likely that cobalt ions are associated with both [Si-0-Al]- and [Al-0-Si-0-AI]2- structures in the zeolite. In the former case, the cobalt cations are assumed to be present as Co2+(OH-) cations and in the latter case as Co2+ cations. The presence of cobalt cations in different environments could account for the appearance of two sets of dinitrosyl bands. The band at 2132 cm-> is present not only on Co-ZSM-5 but also on H-ZSM-5 and Na-ZSM-5, and has been observed by several authors on Cu-ZSM-5 [26-28]. 

In addition it is probable that each absorbance has a shoulder on the short wavelength side of the maximum. Application of Sorenson s data would associate the peaks at 590, 660, 730 and 790 nm with ions derived from pentaenes, hexaenes, heptaenes and octaenes respectively and interconversion of A qq to A660 A,q t0 A730 so on corresPonds to an increase In the length of tne ions by one unit in each case. Wasseiman (41) has also studied polyenic cations derived by protonation oF various polyenes but the reliability of his spectral data has been questioned (40) due to the high reactivity of the species concerned. 

When Fernandez et al. studied partially polymerized Series P PB/PS systems, SANS results yielded peaks in the scattering patterns, see Figure 14 [ ]. Early attempts at understanding these peaks were troublesome due to the multiple causes for such peaks. Later, similar peaks were observed in another set of samples, which were partially swollen, then fully reacted (series S) by An et al. [41], but, in this case, shoulders instead of distinct maximum were observed (Figure 15). In both cases, such maximum or shoulders appeared at mid-range compositions, then were replaced by smoothly decreasing curves on further polymerization of monomer II. 

The 3.5- and 8-ntn nanoparticles show well-resolved peaks at 362 and 473 nm, respectively, as well as other features at higher energies. The 4.5-nm particles show a well-resolved peak at 400 nm and a shoulder at 450 nm. It is tempting to assume that in each case, the lowest energy absorption corresponds to the lowest allowed transition (the A exciton) in bulk M0S2. Polarization spectroscopy can be used to determine if this is the case. The lowest allowed transitions in bulk material, the A and B excitons, are polarized perpendicular to the crystallographic c axis. If the lowest allowed transition correlates to the A exciton, then it would be expected to also be a planar (xy polarized) oscillator. However, tire results of polarization studies reveal that the actual situation is more complicated. A combination of time-resolved polarized emission and one-color time-resolved polarized absorption (transient bleach) studies facillitate assignment of the polarizations of the observed nanoparticle transitions. The 3.5-nm particles are emissive and the polarization of the several of the lowest transitions may be determined... 

The first chlordane-related mortality was of three wild birds and was recorded between 1978 and 1981 (Blus et al., 1983). The levels of chlordanes and heptachlor epoxide from the two adult male red-shouldered hawks (Buteo lineatus) and an adult female great horned owl (Bubo virginianus) were within the critical lethal range that has been defined by experimental studies (heptachlor epoxide in brain tissue 3.4-8.3 pg g-1 wet wt. oxychlordane in brain tissue 1.1 5.0 pg g-1 wet wt.). The chlordane poisoning of birds has been reported in several studies in the United States (Blus et al., 1983, 1985 Post, 1951 Stansley Roscoe, 1999). From 1986 to 1990, 122 cases of avian mortality due to chlordane and/or dieldrin were documented in New York, Maryland and New Jersey (Okoniewski Novesky, 1993). High pesticide concentrations were found in cyclodiene-resistant insect populations. These pesticide-tainted insects, when eaten by birds, caused mortalities in the avian populations (Okoniewski Novesky, 1993). 

The TPD spectra of three different adsorbate systems, corresponding to zeroth-, first- and second-order kinetics, are shown in Figure 2.9. Each trace corresponds to a different initial adsorbate coverage, as indicated in the figure. The simplest case in TPD corresponds to first-order desorption kinetics, represented by the CO/Rh(lll) series in Figure 2.9 [17, 18]. For CO coverages up to 0.5 monolayer (ML), the CO molecules do not interact on Rh(lll) and the desorption traces all fall in the same temperature range, all with the same peak maximum temperature. Hence, the rate of desorption is proportional to the surface concentration of CO. Above 0.5 ML, CO starts to populate additional sites (from vibrational spectroscopy studies we know that in addition to on-top sites also threefold hollow sites are occupied see Fig. 8.15), and a faster reaction channel for desorption opens up, as seen by the development of a shoulder at lower temperatures [18]. 

Asmus and co workers81 studied the pulse radiolysis of polychlorinated biphenyls (PCB) in N2-saturated DCE solutions. The transient absorption spectrum at 5 /is after a 1 /is pulse showed either two distinct absorption maxima (as, e.g., for 3,3, 4,4 -tetrachloro-biphenyl) or a broad absorption band (in the case of 2,2, 4,4, 5,5 -hexachlorobiphenyl) or a broad maximum with an additional shallow shoulder (for 3,5-dichlorobiphenyl) in the range of 375 130 nm. It appears that the number and position of chlorine substituents determine the absorption category. Another absorption band was indicated in the near IR region, but could not be studied. The observed absorption in the 375-430 nm range is attributed to the radical cations from PCB, formed by charge transfer from the radical cation of the solvent ... 

Whereas the proton transfer does not effect the stochiometry of the final PI when water is eliminated in the imidization reaction (fig. 3F), addition of an excess ODA molecule to polyamic acid could lead to the imine type crosslink formation schematically shown in figure 3G. This would lead to a deficiency of carbonyl oxygen atoms for vapor deposited polyimide and is consistent with our analysis. Mack et al. [16] proposed imine crosslink formation from their Raman spectroscopic studies for vapor deposited polyimides with excess ODA. In accordance with this model we attribute the low binding energy shoulder in the polyimide Nls line (figure 4c) to double bonded nitrogen species. However, the model gives no explanation for the carbonyl deficiency found in spin deposited polyamic acid and polyimide. In this case no excess of ODA is observed and only a very weak shoulder has been reported for the Nls line [4,11]. 

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