Electronic and Infrared Spectroscopy

In this chapter we describe the three most important types of optical spectroscopy ultraviolet (UV) and visible, fluorescence, and infrared. UV and visible spectra can be obtained through the same spectrometer. They differ only in the selection of the wavelength of the incident light UV at 180-400 nm and visible at 400-760 nm. Both UV (and visible) and fluorescence spectra describe the phenomenon of electron excitation namely, a valence electron of a molecule is 

Physical Chemistry of Macromolecules Basic Principles and Issues, Second Edition. By S. F. Sun ISBN 0-471-28138-7 Copyright 2004 John Wiley Sons, Inc. 

TABLE 17.1 Examples of Relationship between Frequency, Wave Number, and Wavelength 

TABLE 17.2 Wavelength of Spectroscopic Regions of Electromagnetic Spectrum 

By contrast, infrared spectra describe the vibration of the atoms (not electrons) around a chemical bond. When the frequency of the incident light (radiation) coincides with the chracteristic frequency of the vibration of a chemical bond, a band (or peak) appears. Infrared spectra are not electronic spectra. 

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In the literature, LB films of chlorophyll a have been investigated by many techniques [21,27,28]. In particular, Chapados et al. [29] have studied the aggregation state of chlorophyll a in LB films with electronic and infrared spectroscopies. Their results suggest many points. First, immediately after the fabrication of the film (time zero) the ketone group C = 0 of one chlorophyll a molecule links to the magnesium of an adjacent chlorophyll a molecule to form a dimer. Each dimer interacts via water with another dimer to... 

Southern CA, Levy DH, Florio GM, Longarte A, Zwier TS (2003) Electronic and infrared spectroscopy of anthranilic acid in a supersonic jet. J Phys Chem A 107(20) 4032-4040... 

The section on Spectroscopy has been expanded to include ultraviolet-visible spectroscopy, fluorescence, Raman spectroscopy, and mass spectroscopy. Retained sections have been thoroughly revised in particular, the tables on electronic emission and atomic absorption spectroscopy, nuclear magnetic resonance, and infrared spectroscopy. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon ICP, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-29, and phosphorus-31. 

Confirmation of the linear arrangement came by physical techniques, especially electron diffraction and infrared spectroscopy. Later the nonequivalence of the nitrogen atoms in diazoaeetic ester was shown by means of labeling. ... 

The most widely used techniques for surface analysis are Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), Raman and infrared spectroscopy, and contact angle measurement. Some of these techniques have the ability to determine the composition of the outermost atomic layers, although each technique possesses its own special advantages and disadvantages. 

The electronic properties of Pd were studied by both physical and chemical techniques X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy using CO and NO as probe molecules... 

Surface spectroscopic techniques must be separated carefully into those which require dehydration for sample presentation and those which do not. Among the former are electron microscopy and microprobe analysis, X-ray photoelectron spectroscopy, and infrared spectroscopy. These methods have been applied fruitfully to show the existence of either inner-sphere surface complexes or surface precipitates on minerals found in soils and sediments (13b,30,31-37), but the applicability of the results to natural systems is not without some ambiguity because of the dessication pretreatment involved. If independent experimental evidence for inner-sphere complexation or surface precipitation exists, these methods provide a powerful means of corroboration. 

The main diagnostic tools employed in studying molecular isomerizations are electronic absorption and infrared spectroscopy. Changes of the molecular conformation can be indicated by variations in energy, intensity, or number of electronic peaks, as well as by shifts, splitting, and appearance-disappearance of vibrational bands. 

A wide variety of instrumental techniques, including X-ray diffraction, thermal analysis, electron microscopy, MAS-NMR and infrared spectroscopy, have been employed at different levels of complexity to investigate the effects of mechanochemical treatment on kaolin. Unfortunately, vibrational spectroscopy has only been used at a superficial level in the study of milled kaolin despite the considerable contribution that it has made to the understanding of the structure and reactivity of kaolin itself. 

The basal spacing (d 001) (DRX-Kristalloflex-805 Siemens) and the surface area (Micromeritics ASAP 2400) was obtained on the solids calcined at different temperatures. X-Ray diffraction patterns have also been obtained after ethylenglycol saturation of selected samples. High resolution transmission electron microscopy (HREM) was performed (Jeol 100 CX Temscan) on ultrathin preparations (LKB Ultratome type 8802A). TPD (NH3) and infrared spectroscopy (pyridine) allowed to evaluate the acid properties of the solid calcined at 4(X) and 600°C. 

The performance of the V-Mg oxide catalyst was found to depend on its composition and the method of preparation. As to the composition, it was found that catalysts containing very small or very large amounts of vanadium were not selective. The better catalysts in terms of both activity and selectivity consisted of from about 10 to 60 wt% V2O5 (35). Analyses of these catalysts by X-ray diffraction, Auger electron spectroscopy, and infrared spectroscopy showed that they contained only two identifiable phases Mg orthovanadate (Mg3(V04)2) and MgO. Since MgO had low activity and poor selectivity under the reaction conditions employed, it was concluded that the active phase was Mg orthovanadate (Mg3(V04)2). Indeed, it was later shown that this compound was a selective catalyst (26). 

Although the majority of the lipids in M. laidlawii membranes appear to be in a liquid-crystalline state, the system possesses the same physical properties that many other membranes possess. The ORD is that of a red-shifted a-helix high resolution NMR does not show obvious absorption by hydrocarbon protons, and infrared spectroscopy shows no ft structure. Like erythrocyte ghosts, treatment with pronase leaves an enzyme-resistant core containing about 20% of the protein of the intact membrane (56). This residual core retains the membrane lipid and appears membranous in the electron microscope (56). Like many others, M. laidlawii membranes are solubilized by detergents and can be reconstituted by removal of detergent. Apparently all of these properties can be consistent with a structure in which the lipids are predominantly in the bilayer conformation. The spectroscopic data are therefore insufficient to reject the concept of a phospholipid bilayer structure or to... 

Graft and block copolymers of cotton cellulose, in fiber, yam, and fabric forms, were prepared by free-radical initiated copolymerization reactions of vinyl monomers with cellulose. The properties of the fibrous cellulose-polyvinyl copolymers were evaluated by solubility, ESR, and infrared spectroscopy, light, electron, and scanning electron microscopy, fractional separation, thermal analysis, and physical properties, including textile properties. Generally, the textile properties of the fibrous copolymers were improved as compared with the properties of cotton products. 

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