Lineshapes, comparison

In order to extract the contributions and dynamics of the ketyl radical and fluoranil anion from the TR spectra obtained with the 416 nm probe wavelength, a deconvolution of the Raman bands were done using a fitting procedure employing a Lorentzian lineshape for the Raman bands of the two intermediates. Figure 3.20 shows a comparison of the best-fit (lines) to the experimental TR spectra (dots) in the left-side spectra and the deconvolution extracted from this best fit for the ketyl radical spectra... 

In Fig. 4 we compare the adiabatic (dotted line) and the stabilized standard spectral densities (continuous line) for three values of the anharmonic coupling parameter and for the same damping parameter. Comparison shows that for a0 1, the adiabatic lineshapes are almost the same as those obtained by the exact approach. For aG = 1.5, this lineshape escapes from the exact one. That shows that for ac > 1, the adiabatic corrections becomes sensitive. However, it may be observed by inspection of the bottom spectra of Fig. 4, that if one takes for the adiabatic approach co0o = 165cm 1 and aG = 1.4, the adiabatic lineshape simulates sensitively the standard one obtained with go,, = 150 cm-1 and ac = 1.5. 

Comparison Between Lineshapes Computed by Aid of the Three Basic Models... 

Figure 3. Comparison of the experimental and theoretical Na2 - Na(3s) + Na(3d) yields as a function of w2. In the calculation, an intermediate v = 33, J = 31, 33 resonance is used and to is fixed at 17,720.7 cm"1. The intensities of the two laser fields are 7(

Figure 8.2.7 Reference deconvolution applied to the methanol peak (a) original peak (b) methanol peak deconvolved to a 2 Hz Lorenzian lineshape (c) gradient-shifted methanol peak (d) gradient-shifted methanol peak deconvolved to the same 2 Hz Lorenzian lineshape (e) comparison of the sub-spectrum of the methanol sample using the subtraction algorithm with (sharp peak) and without (flattened peak) reference deconvolution. Reprinted from Hou, T., MacNamara, E. and Raftery, D., NMR analysis of multiple samples using parallel coils improved performance using reference deconvolution and multi-dimensional methods , Anal. Chem. Acta, 400, 297-305, copyright (1999), with permission of Elsevier Science...

Practical applications of the theory of NMR lineshapes of dynamic spectra can be divided into two general groups. One concerns investigations of intra- and inter-molecular reaction mechanisms. The other deals with the determination of kinetic and thermodynamic parameters for equilibria. In the former case the verification of reaction mechanisms usually consists of qualitative comparisons between experimental spectra and those simulated for various values of the rate constants using either visual inspection or visual fitting. 

Fig. 3. Example spectra from the one-dimensional dipolar-shift experiment taken from reference 7. (a) (Top) Experimental l3C chemical shift anisotropy powder pattern for Ru(C5H5)2 and (below) for comparison, the dipolar shift l3C spectrum for the same compound, (b) Calculated dipolar-shift lineshapes for different angles (indicated) between the lH-13C dipolar and chemical shift anisotropy tensor principal z-axes.

Fig. 9. The solid curve depicts the super-Lorentzian lineshape g(u>) for a single spin species in vesicles according to Eq. (57) for Q -= 100. The frequency scale is given in units of I/T2. The wide skirts on which the sharp line is superimposed are illustrated by the plot of 10g(aj) versus u> (dashed curve). A Lorentzian line (x 10) of width 100/72 is shown for comparison (small-dashed curve). Reproduced with permission from M. Bloom, Chem. Phys. Lipids, 1975, 14, 107. 1975 American Chemical Society.

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