Side band assignment

It is seen that both the powder and the crystal show four distinct peaks, marked 1, 2, 3 and 4 in Fig. 11. The remaining peak(s)are the spinning side bands, as verified by the fact that their relative positions change in proportion to the spinning frequency. The doublet around 250 ppm can be assigned to... 

The corresponding H MAS-NMR spectra for the same samples are presented in Fig. 3a, 3b and 3c, respectively. As shown in Fig. 3a, the FI MAS-NMR spectrum of an unheated sepiolite consists of two distinct proton resonances centered near 0 ppm. A sharp resonance at higher field, which gives rise to only a few spinning side bands, is assigned to... 

In other cases, a baseline corrected peak height for a particular absorber may be employed as a term in the equation. In such a case, the wavelength difference on either side of a peak maximum will affect the contribution of that complex term. That increment or gap, in fact, under such circumstances becomes a part of the calibration. It is as important a contribution to the calibration as the coefficients on the wavelength terms. In this correlation spectroscopy, classical band assignments are not always possible. Little specific near-infrared literature exists in advance of most applications and it is not always possible to predict which wavelengths will produce the best linearity and the best sensitivity for a given analytical problem. In the empirical approach a variety of statistical treatments have been attempted. By far the most... 

Raman spectra of uncoupled OH and OD stretch bands show a pronounced asymmetry on the high energy side (Walrafen, 1973). Analysis of the band shape reveals contributions from two bands assigned by Walrafen to non-hydrogen bonded and hydrogen bonded oscillators. Addition of sodium perchlorate, a water structure breaker, results in an increase in intensity of the high energy component, consistent with an increase in proportion of free OH. 

Figure 3. MAS and CPMAS spectra for ball milled mixtures of ScCl3/LiBH4 in the ratios 1 3, 1 4, and 1 6. Peak assignments were obtained from combined analyses of spectra for all nuclei. In parts (e) and (f) the asterisk ( ) denote spinning side bands of the Sc peak for LiSc(BH4)4 at 109 ppm.

Fig. 26. Deconvoluted FT-IR spectra of SNase (5 % (w/w), pH 5.5) a) as a fimction of pressure at 25 °C and b) as a fimction of temperature (band assignment 1611 cm" side chains, 1627 cm" P-sheets, 1651 cm" a-helices, 1641/1659/1666 cm" disordered structures/tums).

Taking into account that formation of the propiophenone 2 is the most important side reaction, we were interested in determining the exact nature of the active sites responsible for the hydrolysis of the acetal moiety. Aimed at this purpose, a characterization of the Bronsted and Lewis acidity of the centers was accomplished for the HY, ZnHY and ZnNaY samples by means of the pyridine adsorption method. Pyridine when adsorbed on solid acids, shows in the IR spectra specific bands assignable to pyridinium Ion (1540 cm ) and Lewis adducts (1450 cm ), which intensities are directly related to the population of both types of centers... 

Double-resonance Spectroscopy.—A review has been given of double-resonance methods in spectroscopy.378 Attention will be focused here on optically (usually phosphorescence) detected magnetic resonance experiments (ODMR). Microwave-optical double-resonance experiments have been carried out on the spectrum of gaseous N02,379 permitting assignment of the rotational = 0—4 side-bands of the 493 nm band. 

Figure 1. Solid state NMR spectrum of a melamine formaldehyde crossllnked acrylic copolymer coating. The static magnetic field Is 7.0 T and the spinning rage Is S.OKHz Chemical shifts and assignments are given In Table I and features marked with an asterisk are resolved spinning side bands.

The intensities of side-band lines reflect the shape of the static (without rotation) spectrum of solids. If a large single crystal could be obtained and installed (stacked) in the probehead of an NMR spectrometer, a narrow signal would be observed for a particular nucleus the chemical shift will depend on the orientation of the crystal axes with respect to magnetic field. Thus, an assignment of three tensor components with respect to the molecular geometry may be made. In the case of a polyciystalline sample (placed in a... 

Cahill et al. have used variable temperature Li MAS NMR spectroscopy to study the lithium dynamics of monoclinic Li3V2(P04)3 [136]. The three lithium sites at 103, 52, and 17 ppm (labeled Li3, Li2, and Lil respectively) are clearly resolved and unambiguously assigned at a sample spinning speed of 25 kHz and a magnetic field strength of 7 T. The relative intensity of the peaks, including contributions from the respective side-band intensities was 1 1 1, as predicted from the crystal structure. One-dimensional Li MAS NMR spectra taken from 276 to 364 K (see Fig. 8.9) display a linear shift dependence with respect to temperature... 

Figure 3 (A) Schematic representation of a Cs z-PDI molecule with color-coding matching the assignment based on (B) a 2D C H -FSLG-HETCOR correlation spectrum using a ramped CP transfer of 500 ps. The asterisks indicate an artifact from the transmitter (in the middle of the 2D spectrum) and spinning side bands. (C) The experimental Hbr-Hbr DQ sideband pattern is extracted from a 2D DQ-SQ H- H correlation spectrum based on 8 rotor periods of DQ recoupling obtained at 25.0 kHz MAS with the dwell time set to 2.0 ps in the indirect dimension. The Hb- Hbr DQ sideband pattern shows significant two-spin correlation, and the Hb- Hb, intermolecular distance is estimated to be 3.7 0.1 A. All experiments were acquired at 20.0 T. Adapted with permission from Ref [86], Copyright 2009 American Chemicai Society.

Low Frequency Observations for Amorphous Polymers. Many amorphous materials studied by Raman exhibit an extremely broad band in the low frequency region. This is true for polycarbonate, poly(methyl methacrylate), and polystyrene (58). Low frequency Raman bands can potentially provide much information regarding the density of states (directly related to the intensity distribution of the broad Raman active band) as well as anomalous behavior observed for the specific heat (58). Often the separation of main-chain and side-chain bands is important in modeling of specific heat, making careful band assignment extremely meaningful (136,137). This separation is analogous to inclusion of optical... 

---