Line broadening parameter

Answer The data were Mated with an exponential multiplication [before Fourier transformation to improve the signal-to-noise ratio in the frequency spectrum ( 1.3.4). The line broadening parameter used was 1 Hz, forcing a rapid decay of the FID. This gives a greater. linewidth than is imposed by the field homogeneity and relaxation rates,... 

Figure 3.34. Some commonly employed window functions. These are used to modify the acquired FID to enhance sensitivity and/or resolution (lb = line broadening parameter, gb = Gaussian broadening parameter i.e. the fraction of the acquisition time when the function has its maximum value see text)...

The examples in this Chapter clearly demonstrate that a plot of spectroscopic dispersion versus absorption (DISPA) is extraordinarily sensitive to any deviation from Lorentzian line shape. More precisely, the direction of displacement of an experimental DISPA plot from its reference circle is often diagnostic of the line-broadening mechanism, and the magnitude of that displacement is directly related to the magnitude of the line-broadening parameter for that mechanism. Finally, all this information is extracted from a single experimental spectrum. How then should such plots best be applied ... 

The host-guest molecular recognition process was also further substantiated by an intermolecular NOE study between 1 and L-Trp. In that study, the line broadening parameter was set to 4 Hz to minimize the subtraction error. When H8 of 1 was irradiated, weak negative intermolecular NOE signals of L-Trp s Ha,... 

H.M. Rietveld developed a practical method to analyze powder diffraction data. The Rietveld refinement method [6] is based on modeling a diffraction pattern according to structural information available for the phases previously identified in the pattern. This model is calculated by computer software after introduction of some crystallographic data space group symmetry, atomic species and positions within the cell, occupancies, lattice parameters, line broadening parameters, and experimental conditions. The term refinement refers to the cyclic improvement process used in the estimation of the set of parameters that can model the diffraction pattern as close as possible to the observed pattern. Usually, the Rietveld refinement is accomplished by minimizing the sum of the differences of calculated and observed intensities for each angular step of the diffraction pattern and by a... 

The halfwidth is determined by pressure and by power broadening (see Sect. 3.6). From the slope of the straight lines in Fig.12.2 the line broadening parameter in (3.53) can be obtained. Together with line-shift measurements, which yield the second parameter a, (3.55), the interaction potential, dependent on the small polarizability of CH4, can be deduced. 

Figure 9.3 Calculated absorption spectrum of CsCaBr2, Yb using different values for the line broadening parameter. The most intense electronic origins are indicated. Electric dipole forbidden transitions are Indicated with vertical bars...

Once the basic work has been done, the observed spectrum can be calculated in several different ways. If the problem is solved in tlie time domain, then the solution provides a list of transitions. Each transition is defined by four quantities the mtegrated intensity, the frequency at which it appears, the linewidth (or decay rate in the time domain) and the phase. From this list of parameters, either a spectrum or a time-domain FID can be calculated easily. The spectrum has the advantage that it can be directly compared to the experimental result. An FID can be subjected to some sort of apodization before Fourier transfomiation to the spectrum this allows additional line broadening to be added to the spectrum independent of the sumilation. 

In these Lorentzian lines, the parameter x deseribes the kinetie deeay lifetime of the moleeule. One says that the speetral lines have been lifetime or Heisenberg broadened by an amount proportional to 1/x. The latter terminology arises beeause the finite lifetime of the moleeular states ean be viewed as produeing, via the Heisenberg uneertainty relation AEAt >fe, states whose energy is "uneertain" to within an amount AE. 

One of the great advantages of Modulation Spectroscopy is its ability to fit the line shapes of sharp, localized structures, as illustrated in the lower part of Figure 1. These fits yield important relevant parameters, such as the value of the energy gap and the broadening parameter. 

NMR line broadening is a suitable kinetic method for determining activation parameters for Co—C bond homolysis, and gave A//- values in the range 18-22.5 keal mol for a selection of Co(Por)R complexes containing secondary or tertiary alkyl groups.Bond dissociation enthalpies and entropies for several... 

The effect of a pressure of 80 and 150 MPa on the spin-state transition has been also studied [169], a series of spectra obtained at 150 MPa being shown in Fig. 32. The speetra show relaxation effects as line broadening and linewidth asymmetry. Calculated spectra were obtained in the same way as at ambient pressure. Rate constants for a number of temperatures are listed in Table 12, the parameter values resulting from an Arrhenius plot of the rate constants being listed in Table 13. In Fig. 33, the quantity 5g of Eq. (36) has been plotted as a... 

Here, ojr is the rate of spinner rotation. I is the proton spin number, 8 is the chemical shift anisotropy (CSA) and q is the asymmetric parameter of the CSA tensor. Thus, the line broadening occurs when an incoherent fluctuation frequency is very close to the coherent amplitude of proton decoupling monotonously decreased values without such interference in Figure 1. 

DR. SWADDLE Yes, that is correct. As I stated, we have been careful to work in areas where at least 90 percent of the line broadening is controlled by solvent exchange. I think John Hunt is the person to comment on what happens to the other NMR parameters under pressure. I believe he has found some pressure-dependence of T. ... 

---