Narrow signals spectra

MeOAn-ANI-3 NI in the nematic liquid crystal mixture E-7 (Merck) at two orientations of the liquid crystal director, L, taken 700 ns after a 420 nm laser pulse at 150 K. The narrow signal is an expansion of the radical pair signal, (b) Numerical differentiation of the B L L spectrum. 

The general construction of an atomic absorption spectrometer, which need not be at all complicated, is shown schematically in Fig. 1. The most important components are the light source (A), which emits the characteristic narrow-line spectrum of the element of interest an absorption cell or atom reservoir in which the atoms of the sample to be analysed are formed by thermal molecular dissociation, most commonly by a flame (B) a monochromator (C) for the spectral dispersion of the light into its component wavelengths with an exit slit of variable width to permit selection and isolation of the analytical wavelength a photomultiplier detector (D) whose function it is to convert photons of light into an electrical signal which may be amplified (E) and eventually displayed to the operator on the instruments readout, (F). 

As is generally known, electron spin resonance reveals the presence of unpaired electrons. This is of course characteristic of free radicals and the most well known stable free radical is a, a-diphenyl-0-picrylhydrazyl(DPPH) (1,213). In the ESR spectrum it gives a narrow signal close to free spin value g 2.0036 and is used for calibrating the magnetic field (2). 

Fig. 3.3.5 H decoupled C spectra of isotactic polypropylene for different spinning frequencies o>r =l7tv and orientation angles i/r of the rotation axis, (a) Static sample. The wideline resonances of the different carbons overlap, (b) MAS spectrum with fast sample spinning. Narrow signals are observed at the isotropic chemical shifts only, (c) MAS spectrum with slow sample spinning. In addition to the centre line, sideband signals are observed at seperations naiR from centre lines, (d) OMAS spectrum with fast sample spinning. The orientation of the axis deviates from the magic angle. Each resonance forms a powder spectrum with reduced width, which can serve as a protractor (cf Fig. 3.1.3). Adapted from [Blu4] with permission from Wiley-VCH.

An application of the saturation-recovery filter to the suppression of signal from rigid components in bisphenol-apoly(carbonate) is shown in Fig. 7.2.2 [Hanl]. The wideline solid-echo spectrum of the phenyl deuterons exhibits a range of broad and narrow components (a) as a result of a distribution of motional correlation times. The mobile components are characterized by a shorter T than the more rigid components. Consequently the rigid components can be suppressed by partial saturation. After application of the saturation-recovery filter the shape of the wideline spectrum is dominated by the narrow signal in the centre from the mobile ring deuterons (b). 

Fig. 16. Experimental C direct excitation spectra of an aqueous dispersion of poly-u-butylcyanoacrylate nanocapsules (top) and of reference samples of liquid and dissolved constituents (a aqueous solution of the block-copolymer surfactant Pluronic F68 b the liquid oil component Miglyol 812 used as capsule content c the liquid monomer u-butylcyanoacry-late). " All spectra are measured at a resonance frequency of wc 100MHz under full proton decoupling. In the spectrum of the dispersion, no narrow signals occur at the positions of the n-butylcyanoacrylate resonances (vertical arrows), indicating the complete absence of the monomer after the formation of the capsules. For the capsule dispersion, a slight increase in line width is observed for the characteristic resonances of the liquid components.

Fig. 35. C-NMR-spectra of aqueous dispersions of poly- -butylcyanoacrylate nanocapsules after 3 h of annealing at different temperatures (a) 50°C, (b) 100°C, (c) 130°C. The ( H)- C crosspolarization spectra (tcp = 1 ms, left column) indicate the loss of the solid capsule wall at higher temperatures (see also Fig. 36). The narrow signals superimposed on the solid-state spectrum of the polymer derive partially from the adsorption of the triglyceride oil and the surfactant to the capsule surface (compare Section 4.4), partially from the residual cp in the liquid phase. The direct excitation spectra (right column) show the liquid and dissolved components with an increasing indication for traces of the n-butylcyanoacrylate monomer which results from depolymerization of the capsule wall material (arrows, see also Fig. 37). ...

Most data were obtained by measurements of H NMR spectra of 15NQ-labelled compounds.30,49-52,60-68 In some cases (sufficiently high value of 7(15NQ, H)exp and relatively narrow signal of exchanging proton), it is possible to observe 0.18% natural abundance 15N satellites in the H NMR spectrum of non-labelled compounds.46 Figure 4 shows 15N INEPT spectrum of compound 48 measured at the natural abundance level of 15N from which 7(15N . H)exp can be read. 

In poloxamer, a synthetic block copolymer of ethylene oxide (EO) and propylene oxide (PO) (USP XXIII, NF18), the oxypropylene/oxyethylene ratio is determined using a H NMR spectrum measured in CDCI3. The oxypropylene units are characterized by a narrow signal at about 1.1 ppm due to the CH3 group. The CH2O/CHO units cause a multiplet between 3.2 and 3.8 ppm. The percentage of oxyethylene can be calculated from the equation... 

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... 

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