Wide lines

Poly(vinyl fluoride) [24981-14-4] (PVF) is a semicrystaltiae polymer with a planar, zig-zag configuration (50). The degree of crystallinity can vary significantly from 20—60% (51) and is thought to be primarily a function of defect stmctures. Wide-line nmr and x-ray diffraction studies show the unit cell to contain two monomer units and have the dimensions of a = 0.857 nm, b = 0.495 nm, and c = 0.252 nm (52). Similarity to the phase I crystal form of poly (vinytidene fluoride) suggests an orthorhombic crystal (53). 

In crystallizing fatty acids, solvent polarity does not influence crystal form as much as temperature and concentration (9). Infrared (9,10) and wide-line nmr spectra (11) as well as x-ray methods (12,13) can be used to detect the various crystalline forms. 

Sample preparation requirements in solid state NMR are strikingly simple because the measurement is carried out at ambient temperature and pressure. Wide-line NMR experiments can be carried out on solid samples in any form, as far as the sample dimensions fit those of the coil in the NMR probe. MAS experiments require the material to be uniformly distributed within the rotor. 

Fig. la-c. Theoretical 2H NMR line shapes for axially symmetric FGT (r = 0) in rigid solids, cf. Equ. (1). a Line shapes for the two NMR transitions b 2H spectrum (Pake diagram) in absorption mode as obtained by Fourier transform methods c 2H spectrum in derivative mode as obtained by wide line methods... 

The number of the constraints to chain mobility shown in Fig. 16 decreases with increasing temperature, reflecting the increase of the free volume. From a comparison of the spectra in Fig. 15 with line shapes calculated for flexible chains on a diamond lattice 23 (one can infer that the average length of the flexible unit increases from 3-5 bonds at room temperyture to about 10-15 bonds at 380 K. Our model thus can quantitatively explain the gradual increase of the number of conformations accessible to the chain motion. The earlier XH wide line data 72 are also in accord with our findings. 

Another point of contention has been the extent to which, if any, SbFj is reduced to SbFs upon intercalation. Although chemical analyses have shown an F Sb ratio of 5 1 (Lll, M5), Sb Mossbauer measurements (B24) indicated partial reduction of Sb(V) to Sb(III). On the other hand, mass-spectral measurements as a function of temperature (S15) showed only SbFs, evolved in stages, with no fluorocarbons emitted at any time. The latter are usually an indication of partial reduction of the intercalant and fluorination of the graphite host. Wide-line, F-NMR chemical-shifts are consistent with either SbFj or SbFe, but not with SbFs, but the occurrence of fluorine exchange could produce minor amounts of trivalent species (FI 1) this point is thus still controversial, and will be alluded to again. 

Magnetic-susceptibility measurements showed the presence of UF4 in heated samples. Ebert et al. (E14) reported a nominal stoichiometry CisUFg, magnetic-susceptibility measurements indicating partial reduction at room temperature, with 10% of the uranium species present as U(IV). Wide-line NMR demonstrated the presence of both U(VI) and U(IV). 

Ultraviolet resonance Raman Wide-line separation Wild type... 

In the solid, dynamics occurring within the kHz frequency scale can be examined by line-shape analysis of 2H or 13C (or 15N) NMR spectra by respective quadrupolar and CSA interactions, isotropic peaks16,59-62 or dipolar couplings based on dipolar chemical shift correlation experiments.63-65 In the former, tyrosine or phenylalanine dynamics of Leu-enkephalin are examined at frequencies of 103-104 Hz by 2H NMR of deuterated samples and at 1.3 x 102 Hz by 13C CPMAS, respectively.60-62 In the latter, dipolar interactions between the 1H-1H and 1H-13C (or 3H-15N) pairs are determined by a 2D-MAS SLF technique such as wide-line separation (WISE)63 and dipolar chemical shift separation (DIP-SHIFT)64,65 or Lee-Goldburg CP (LGCP) NMR,66 respectively. In the WISE experiment, the XH wide-line spectrum of the blend polymers consists of a rather featureless superposition of components with different dipolar widths which can be separated in the second frequency dimension and related to structural units according to their 13C chemical shifts.63... 

Molecular Motions and Dynamic Structures. Molecular motions are of quite general occurrence in the solid state for molecules of high symmetry (22,23). If the motion does not introduce disorder into the crystal lattice (as, for example, the in-plane reorientation of benzene which occurs by 60° jumps between equivalent sites) it is not detected by diffraction measurements which will find a seemingly static lattice. Such molecular motions may be detected by wide-line proton NMR spectroscopy and quantified by relaxation-time measurements which yield activation barriers for the reorientation process. In addition, in some cases, the molecular reorientation may be coupled with a chemical exchange process as, for example, in the case of many fluxional organometallic molecules. ... 

Eads, T.M. 1995. Wide-line and high-resolution 1H NMR of food materials. In Annual Reports on NMR Spectroscopy (G.A. Webb, P.S. Belton, and M.J. McCarthy, eds), Vol. 31, pp. 143-156. Academic Press, New York. 

Although the single-layer negative resists commonly utilized are simple, they typically do not resolve narrow (0.5 ftm) gaps between wide lines or pads due to proximity effects from backscatter from the substrate during electron beam (E-beam) exposure. Further, there are variations in linewidth which occur when images are written in a single-layer resist which overlies steps in the substrate. 

Zeigler, R.C. and Maciel, GE., A study of the structure and dynamics of dimethyloctadecylsilyl-modified silica using wide-line NMR techniques, J. Am. 

For quadrupolar nuclei, rapid pulsing can improve the signal-to-noise ratio. They are often most readily measured by vidde-line techniques however, as for example (84) and N (79). Many more wide-line measurements have been made of N, which is quadrupolar, than high-resolution measurements of N, which has spin but is expensive. The broadening increases with the nuclear quadrupole moment, which is small for (2.8 x 10 ), Li (4.6 x 10 ), and (—4 x 10 ), and fairly small, between 10 and 10 , for Be, B, N, S, C1, and C1 (the units are e x 10 cm, where e is the electronic charge) (20, 70). The broadening increases with asymmetry of the nuclear environment thus, the line width increases a thousand-fold from the relatively sharp line... 

A number of works have focused on the pattern dependencies in tungsten (both tungsten via and local interconnect) polishing [12,19,21]. To first order, empirical results seem to suggest that dishing is dominated by the width or size of the metal feature being polished wide lines tend to suffer... 

Figure 8. Fine lines in cross-linked methacrylate resist film cured at I00°C for 1 h, exposed at 3.2 fC/cm at 20 kV, and developed jor 5 min in methyl isobutyl ketone. Key a, 1.5-ym and S-ym wide lines (S) and b, I-yjn wide lines.

The commercial value of high-performance polymers, i.e., polymers of high molecular weight, which may be composite structures and do not dissolve, have driven the development of new methods for material characterization. Solid-state NMR spectra can be acquired in either high resolution or wide-line mode, methods that yield complementary information [8,13,19,23]. Solid-state NMR has the advantage of being able to analyze the material as received consequently, it... 

With the two layer resist process, no effect of the surface structure is observed in the resulting resist pattern. A 0.35 wide lines with an aspect ratio of 6 have almost vertical side-walls and show a linewidth loss less than 0.1 iim by the etching of 2.0 thick AZ layer. In spite of the thin film of SNR, pin-holes were hardly observed in the dry-etched AZ patterns, presumably due to good wettability of silicone resin on organic film surface. 

The NMR measurements were carried out by the wide-line unit of a Varian DP 60 spectrometer. A frequency of 16 MHz and a modulation frequency of 20 Hz were used throughout. The amplitude of the modulation was adapted to the width and the intensity of the observed lines. For weak lines, the effect of modulation broadening was carefully checked and corrected following procedures outlined by Kroon (21). 

Usually, in wide-line NMR experiments, the first derivative of the resonance absorption curve is obtained. Taking into account that the amplitude of this curve decreases with the square of the line width, the conclusion can be drawn from Table I that, besides the resonances from the Si sites, the contributions of the other sites should be hidden in the noise during measurement. 

An extension of these measurements to other types of zeolites yielded bend temperatures and activation energies ranging from 120° to 200° C and 5-10 kcal/mole. The shape of the wide line signals of OH groups in zeo-... 

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