Line width origin

The origin of the line widths of coals is attributed mainly, e.g. by Sullivan 52,53) and Maciel50), to the distributions of similar structures and chemical shifts. 

Abstract Sonoluminescence from alkali-metal salt solutions reveals excited state alkali - metal atom emission which exhibits asymmetrically-broadened lines. The location of the emission site is of interest as well as how nonvolatile ions are reduced and electronically excited. This chapter reviews sonoluminescence studies on alkali-metal atom emission in various environments. We focus on the emission mechanism does the emission occur in the gas phase within bubbles or in heated fluid at the bubble/liquid interface Many studies support the gas phase origin. The transfer of nonvolatile ions into bubbles is suggested to occur by means of liquid droplets, which are injected into bubbles during nonspherical bubble oscillation, bubble coalescence and/or bubble fragmentation. The line width of the alkali-metal atom emission may provide the relative density of gas at bubble collapse under the assumption of the gas phase origin. 

In the paramagnetic regime, the evolution of the EPR line width and g value show the presence of two transitions, observed at 142 and 61 K in the Mo salt, and at 222 and 46 K in the W salt. Based on detailed X-ray diffraction experiments performed on the Mo salt, the high temperature transition has been attributed to a structural second-order phase transition to a triclinic unit cell with apparition of a superstructure with a modulation vector q = (0,1/2, 1/2). Because of a twinning of the crystals at this transition, it has not been possible to determine the microscopic features of the transition, which is probably associated to an ordering of the anions, which are disordered at room temperature, an original feature for such centrosymmetric anions. This superstructure remains present down to the Neel... 

A general observation from the HNMR studies on micelle-encapsulated heme is that the line width of the heme protons increases significantly in the micellar solutions compared to those in simple solutions. The change in linewidths of heme methyl protons in micelles is not as large in low-spin Fe(III) hemes as in the high-spin ones. The linewidths in four-coordinate and five-coordinate complexes of ferrous hemes in aqueous micellar solutions are also quite broad compared to those observed in benzene solutions [12, 61], but are similar to those of hemoproteins [2,62]. We examine below the origin and implications of the linewidth change in micellar solutions. 

The activation parameters are subjected to errors, especially in the precise determination of temperatures such as Tc, the frequency separation (Av), line widths, coupling constants, variation of the concentration with the temperature etc. Although the experimental determination of the activation parameters could have been performed accurately, it should not be pretended to possess excessive accuracy. Caution is advised especially with entropies of activation, due to the inherent imprecision of the method (ordinates at the origin from least-squares line fitting) ... 

Figure 13.2—Simplified schematic of an atom showing the origin, and the Siegbahn nomenclature, of some fluorescence radiation processes caused by impact of a photon having a high energy. The position of the spectral line is not significantly influenced by the chemical combination in which the atom is found. For example, the Kat line from sulphur is observed at 0.5348 nm for S + and at 0.5350 nm for S°, yielding a shift of 1 eV, which is comparable to the natural line width for X-rays.

One of the most striking properties of humic acid is its change in free radical content upon conversion to the solid sodium salt. This change is reversible upon reacidification of the salt, the spin content returns to its original level (28). In general, the line widths increased about 50% on conversion to the salt. Table III illustrates this effect for many different humic acids. These results seem entirely consistent with the known properties of the salts of quinhydrone as shown in Figure 6 (28). 

The first 27A1 MAS NMR study of zeolites was carried out by Freude and Behrens (151). They measured, first, chemical shifts and half-widths of signals from stationary samples of zeolites Na-A, Tl-A, Na-Y, and Tl-Y at 16 MHz. For MAS frequencies of vR such that vR > Vq/vl the central line of the 27A1 resonance is reduced to about j of its original value. Freude and Behrens next calculated the quadrupole frequencies vQ and shifts of the center of gravity of each line due to the quadrupole interaction, i.e., vQ = (v - vL)/vL at 70 MHz. Then, apparent line positions and line widths, S and <5v 2MAS, were measured experimentally using MAS at 70 MHz. The corrected chemical shift value at 70 MHz was then calculated from the relationship <5, = 5ex — <5q. They were several ppm different from the apparent values (see Table XII). 

The ESR spectra of HAs and FAs of any nature and origin, including native soils, organic amendments, and amended soils, show a sharp and narrow resonance characterized by a g value at about 2.0040 and by a line width ranging from 0.60 to 0.80 mT, which is attributed to indigenous organic free radicals of semiquinonic... 

---