Band-fitting software

Once a model has been calculated from the information available, it should not be accepted at face value but should be validated by assignment of all the calculated bands in the overlapped band. This, of course, is not an easy task and must be undertaken with care to validate the model. Users of band-fitting software should also recognize that their own biases may well be incorporated in their selection of the initial parameters, the number of bands contained within the multiplet that is being modeled, and the assignment of all bands used to fit the multiplet. 

In figure 12.19 the contributions of the three bands in the silane stretching region (established by curve fitting software) are correlated versus the percentage of secondary species on the surface, as determined by NMR. 

Band fitting (curve fitting, or band shape analysis) is conveniently performed with commercially available software packages which fit, interactively or automatically, Gaussian or Lorentzian line shapes (or their combinations) to an unknown band profile. The applicability of this technique to lignin chemistry is not known at present. 

To demonstrate calibration linearity and transferability using a fiber-optic probe and simple peak-area methods, the solution spectra of four solutions of phenylisocyanate in acetone were used. The mid-infrared spectrum of most isocyanates are characterized by a sharp band, sometimes exhibiting shoulders, at 2250-2285 cm which is assigned to the asymmetric stretch of the -N C=0 group. In the spectra of acetone solutions of phenylisocyanate, this band appears at 2261 cm with a substantial shoulder at 2283 cm. Figure 1 shows an expanded view of the band, displayed in a screen shot from the GRAMS peak-fitting software with two Lorentzian peaks fitted at 2261 and 2283 cm. ... 

The summation runs over all the absorption bands (with wavenumber Vq and experimental dipole strength Oexp) which contribute to the complex band structure. Y, D xp total dipole strength of the complex band. In practice, v is determined by curve-fitting software by placing a line shape function under the complex band. Vq is equal to the sum of the peak maxima Vq weighted by the fractional contribution Xj (0 1, X, x,- = 1)... 

Modem pRS systems are accompanied with powerful spectral acquisition and analysis software, which enables the creation of ID (cross section), 2D, and 3D maps of various features from the ID, 2D, or 3D array of spatially resolved Raman spectra. Various features that can be routinely mapped include intensity variations of specific peaks (by plotting the user-defined peak intensity or integrated area under the peak), intensity ratio of two different bands, peak position (by user-defined peak fitting routines such as Gaussian, Lorentzian), and peak widths. The obtained images can be further processed to highlight the spatial variations of the acquired spectra. For example. Boolean maps, which present a binary... 

Method A uses bulk ATR spectra of thick polycrystalline samples of PEG with a random orientation of helical coils Using the SpectraRay 2 software package (SENTECH Instruments GmbH, Berlin, Germany), Drude-Lorentz oscillator parameters [15] were determined by spectral line fits to selected vibrational bands of an ATR spectrum, taken from... 

To evaluate complex band envelopes and to identify underlying component bands of the spectra, it is often necessary to perform classical curvefitting procedures, using for instance an iterative least-squares curve-fitting procedure such as that proposed in the Peakfit (San Rafael, CA) software. The best fit of the experimental data may be obtained by varying the frequency, bandwidth and intensity of the bands. In most cases it is appropriate to employ Gaussian band shapes. 

Fig. 4 Si mutations of the distance distribution broadening for the Gd(iii) complexes with D = 1500 MHz and a single Gd(iii)-nitroxide distance of 3 nm at X band (A) simulated DEER trace (solid line) and its fit with DeerAnalysis software (dashed line) (B) resulting distance distribution (dotted vertical line indicates the single distance input). Data from ref. 36.

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