Experimental methods resonance

Leniart D S 1979 Instrumentation and experimental methods in double resonance Multiple Electron Resonance Spectroscopy ed M M Doric and J H Freed (New York Plenum) ch 2, pp 5-72... 

For both copolymers and stereoregular polymers, experimental methods for characterizing the products often involve spectroscopy. We shall see that nuclear magnetic resonance (NMR) spectra are particularly well suited for the study of tacticity. This method is also used for the analysis of copolymers. 

It can be seen from Figures 3.7 and 3.8 that the calculations reproduce very well not only the experimental spectra but also the experimentally observed isotopic shifts indicating a high reliability of the computational method. According to this comparison, definite attribution can be made for even the difficult Raman bands that cannot be assigned based solely on the experimental results. It is, however, necessary to mention at this point that the calculated Raman spectrum provided directly by the ab initio computations correspond to the normal Raman spectrum with the band intensity determined by the polarizability of the correlating vibration. Since the intensity pattern exhibited by the experimentally recorded resonance Raman spectrum is due to the resonance enhancement effect of a particular chromophore, with no consideration of this effect, the calculated intensity pattern may, in many... 

In the case of heterogeneous polymers the experimental methods need to be refined. In order to analyze those polymers it is necessary to determine a set of functions / (M), which describe the distribution for each kind of heterogeneity i This could be the mass distributions of the blocks in a diblock copolymer. The standard SEC methods fail here and one needs to refine the method, e.g., by performing liquid chromatography at the critical point of adsorption [59] or combine SEC with methods, which are, for instance, sensitive to the chemical structure, e.g., high-pressure liquid chromatography (HPLC), infrared (IR), or nuclear magnetic resonance spectroscopy (NMR) [57],... 

Several mechanisms are involved in the permeability through Caco-2 cells. In order to obtain a more pure measure of membrane permeability, an experimental method based on ghost erythrocytes (red blood cells which have been emptied of their intracellular content) and diffusion constant measurements using nuclear magnetic resonance (NMR) has been proposed [108]. 

The preferred conformations of methoxy groups attached to aromatic rings in the phenethylamines have recently been investigated using theoretical approaches, gas phase experimental methods, and nuclear magnetic resonance (NMR) techniques for the molecules in aqueous solution. Ab initio theoretical calculations and experimental gas phase results have indicated that when two... 

The experimental methods in ENDOR spectroscopy have been extensively described by Kevan and Kispert4) in their monograph, Electron spin double resonance spectroscopy, and by Leniart18 in a recent paper. In this section we shall briefly review the instrumentation used in solid state ENDOR and describe the technical details of some new experimental methods. 

Magnetic resonance techniques have again been popular for studying enzymes which are involved in phosphate hydrolysis and transfer. 31P or 19F N.m.r.1-2 and spinlabelling3 have all been used to study the interaction of substrates with these enzymes, while affinity labelling4 5 6 7 is another technique which has been used to obtain information about the sequence and conformation of amino-acid chains at the active sites of enzymes. Recently, these experimental methods have been applied to the study of cell membranes,6-7 and these are mentioned in a new series of books concerned with enzymes in biological membranes.8 A new journal, Trends in Biochemical Sciences, which contains concise, up-to-date reviews on these and other topics is published by Elsevier on behalf of the International Union of Biochemistry. 

In the present review, a new variation on an existing experimental method will be used to show how accurate unimolecular dissociation rate constants can be derived for thermal systems. For example, thermal bimolecular reactions are amenable to study by use of several, now well-known, techniques such as (Fourier transform) ion cyclotron resonance spectrometry (FTICR), flowing afterglow (FA), and high-pressure mass spectrometry (HPMS). In systems where a bimolecular reaction leads to products other than a simple association adduct, the bimolecular reaction can always be thought of as containing a unimolecular... 

The electron density centered at M is the only central contributor at the nuclear position M, as in this case the nucleus coincides with the field point P, which is excluded from the integrals. For transition metal atoms, the central contributions are the largest contributors to the properties at the nuclear position, which can be compared directly with results from other experimental methods. The electric field gradient at the nucleus, for instance, can be measured very accurately for certain nuclei with nuclear quadrupole resonance and/or Mdssbauer spectroscopic methods, while the electrostatic potential at the nucleus is related to the inner-shell ionization energies of atoms, which are accessible by photoelectron and X-ray spectroscopic methods. 

Depending on the computational or experimental methods and models used, various resonance structures have been proposed for FeNO 7 complexes, such as Fe(II)-NO°, Fe(III)-NO- (metal-to-ligand charge transfer) or Fe(I)-NO+ (ligand-to-metal charge transfer). It has been pointed out previously that DFT-computed spin densities of FeNO 7 complexes are extremely sensitive to the choice of functional. The reported values are summarized in Table V. 

Considering that the literature on the development of experimental methods and important fields of application of X/Y correlations in inorganic, organoelement and organometallic chemistry up to 1997 has been covered in earlier reviews,11 we will focus here on recent improvements of experimental techniques and novel applications for compound characterisation. Despite the recently increasing interest in the application of X/Y correlation spectroscopy in solids,12,13 this review will cover only solution NMR techniques. Likewise, a survey of specialised triple-resonance NMR experiments devoted to the characterisation of bio-molecules, and their application, is considered beyond the scope of this article. 

Coherent Raman detected EPR spectroscopy is a new experimental method which combines optical and EPR transitions. It was applied for the first time to a bioinolecule, azurin. The information obtained allows to test electronic and structural models of the Cu site to be probed.23 In a subsequent report the same group of authors has applied microwave modulated circular dichroism to unravel individual resonance lines in overlapping spectra and to assign them to specific electronic transitions.24... 

Fig. 5. Energy above the valence band of levels reported in the literature for GaP. Arrangement and notations are the same as in Fig. 4. Abbreviations for experimental methods not defined in Fig. 4. are temperature dependence of resistivity (RT), temperature dependence of minority-carrier lifetime (LT), Hall effect (H), and photostimulated electron paramagnetic resonance (PEPR).

Various experimental methods have been developed for investigating the magnetoelastic properties of thin films and nanoscale magnetic systems. In the following subsections, we discuss the most important ones (i) the magnetoelastic cantilever, (ii) strain induced anisotropy, (iii) magnetostriction in spin valves, (iv) strain modulated ferromagnetic resonance, (v) secondary-electron spin-polarisation, and (vi) strain-induced anisotropy due to the spontaneous strains. 

Traditionally, charge transfer mechanisms have been studied by such methods as conductivity, the Hall effect, and thermoelectric effect. Details of these applications may be found in Experimental Methods of Physics, Vol. 6, Pt. b (12), the article on ionic conductivity by Lidiard (70), and in many of the original papers quoted. More recently, techniques such as electron spin resonance (13), dielectric loss and pulsed photoconductivity methods (5—8) have been used to study semiconduction in organic materials. 

Related classes of gitonic superelectrophiles are the previously mentioned protoacetyl dications and activated acyl cationic electrophiles. The acyl cations themselves have been extensively studied by theoretical and experimental methods,22 as they are intermediates in many Friedel-Crafts reactions. Several types of acyl cations have been directly observed by spectroscopic methods and even were characterized by X-ray crystal structure analysis. Acyl cations are relative weak electrophiles as they are effectively stabilized by resonance. They are capable of reacting with aromatics such as benzene and activated arenes, but do not generally react with weaker nucleophiles such as deactivated arenes or saturated alkanes. 

Lambert, J.B., Holland, L.N., and Mazzola, E.P., Nuclear Magnetic Resonance Spectroscopy Introduction to Principles, Applications and Experimental Methods, Prentice Hall, Englewood Cliffs, NJ, 2003. 

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