Infrared laser Raman spectroscopy

Although both of these spectroscopic methods have a wide use in their own right, the example given below demonstrated well the complementary value of the two methods, taking advantage of the fact that elements of high atomic number, eg. antimony and bromine, have relatively more intense Raman spectra but the lighter elements show up clearly in the infrared spectra. 

An example of the application of these techniques is the identification of additives in PVC. When a sample of PVC was examined by infrared spectroscopy the strongest bands (9.8 and 14.9 um) were due to a talc type material and bands of medium intensity were assigned to polypropylene and possibly antimony trioxide (13.4 um). Additional weak bands in the 7.3 - 7.7 um region were possibly due to decabromodiphenyl ether. In the Raman spectrum, however, the strongest bands (250 and 185 cm shift) confirmed the presence of antimony trioxide and some bands of medium intensity confirmed the presence of decabromodiphenyl ether (doublet at 140, triplet at 220 cm -l shift) and polypropylene (800, 835, 1150, 1325, 1450 and 2900 cm -1 shift). The silicate bands that obscured the regions of the infi ared spectrum were not observed in the Raman Spectrum. 

Examples of other spectroscopic techniques that have been applied to the identification of additives in polymers are given in Table 5.7. 

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Qu JNY, Wilson BC, Suria D. Concentration measurements of multiple analytes in human sera by near-infrared laser Raman spectroscopy. Applied Optics 1999, 38, 5491-5498. 

Vibrational Spectroscopy. Infrared absorption spectra may be obtained using convention IR or FTIR instrumentation the catalyst may be present as a compressed disk, allowing transmission spectroscopy. If the surface area is high, there can be enough chemisorbed species for their spectra to be recorded. This approach is widely used to follow actual catalyzed reactions see, for example. Refs. 26 (metal oxide catalysts) and 27 (zeolitic catalysts). Diffuse reflectance infrared reflection spectroscopy (DRIFT S) may be used on films [e.g.. Ref. 28—Si02 films on Mo(llO)]. Laser Raman spectroscopy (e.g.. Refs. 29, 30) and infrared emission spectroscopy may give greater detail [31]. 

A small but artistically interesting use of fluorspar is ia the productioa of vases, cups, and other ornamental objects popularly known as Blue John, after the Blue John Mine, Derbyshire, U.K. Optical quaUty fluorite, sometimes from natural crystals, but more often artificially grown, is important ia use as iafrared transmission wiadows and leases (70) and optical components of high energy laser systems (see Infrared and RAMAN spectroscopy Lasers) (71). 

Fia. 13. (a) Raman spectrum of a pretreated Cab-O-Sil disk recorded using a laser beam expander (b) infrared spectrum of a newly pressed Cab-O-Sil disk. From Hendra and Gilson, Laser Raman Spectroscopy, p. 186. Wiley, New York, 1970. 

Earlier in this review, the relationship between the Raman and infrared spectra of molecules possessing high or low symmetry was considered. It was indicated that for molecules possessing a center of symmetry, no vibration is active in both the Raman and infrared spectra. Several adsorbates in this category and one of intermediate symmetry have been studied by laser Raman spectroscopy (Table IX), and most of these spectra are considered in this section. 

The vibrations of molecular bonds provide insight into bonding and stmcture. This information can be obtained by infrared spectroscopy (IRS), laser Raman spectroscopy, or electron energy loss spectroscopy (EELS). IRS and EELS have provided a wealth of data about the stmcture of catalysts and the bonding of adsorbates. IRS has also been used under reaction conditions to follow the dynamics of adsorbed reactants, intermediates, and products. Raman spectroscopy has provided exciting information about the precursors involved in the synthesis of catalysts and the stmcture of adsorbates present on catalyst and electrode surfaces. 

Our objective in this article is not to introduce the theory of Fourier transform-infrared or laser-Raman spectroscopy this has already been done for F.t.-i.r. in such books as those of Griffiths,21 Ferraro and Basile,22 and... 

Progress in the Raman spectroscopic study of carbohydrates became possible during the past few years owing to the introduction of laser sources. Before discussing the results of laser-Raman spectroscopy applied to carbohydrates, we shall give a brief recapitulation of the physical principles of the Raman effect. Experimental techniques of infrared spectroscopy have been described in previous reviews,116,17 but no such description has been given for the Raman method. That is why the Description Section, which follows, will include the physical fundamentals of the method, as well as the sampling techniques. 

It may be concluded, from the analysis of the Raman results, that the information provided by Raman spectroscopy is, in essence, similar to that of infrared spectroscopy. The exploitation of the data, namely, the frequencies and intensities due to the molecular vibrations, is of a certain benefit in giving some insight as to the conformations of carbohydrates, and their interactions with the environment. As laser-Raman spectroscopy is applicable to solids, as well as to aqueous solutions, the linear relationship between Raman intensities and mass concentrations, and the specificity and high quality of the spectra experimentally obtained, make this technique particularly promising in investigations of the chemistry and biochemistry of carbohydrates. 

Laser Raman spectroscopy is well suited for the study of air-sensitive liquids because the sample may be contained in an all-glass cell.21 Such a cell is much easier to load on a vacuum line and to maintain leak-free than is an infrared cell. Also, such a tube is easier to heat or cool than the typical IR cell. 

Table VI A comparison of Infrared and Laser Raman Spectroscopy for the Characterization of solid/liquid Interfaces...

Methods such as nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA), electron spin resonance (ESR), infrared (IR), and laser raman spectroscopy could be used in conjunction with rate studies to define mechanisms. Another alternative would be to use fast kinetic techniques such as pressure-jump relaxation, electric field pulse, or stopped flow (Chapter 4), where chemical kinetics are measured and mechanisms can be definitively established. 

Laser Raman spectroscopy mass spectrometry vibrational quantum number near infrared... 

Figure 3.4-1 Optical diagram of a commercial Michelson interferometer for infrared and Raman spectroscopy (Bruker IFS 66 with Raman module FRA 106). CE control electronics, D1/D2 IR detectors, BS beamsplitter, MS mirror scanner, IP input port, S IR source, AC aperture changer, XI — X3 external beams, A aperture for Raman spectroscopy, D detector for Raman spectroscopy, FM Rayleigh filter module, SC sample compartment with illumination optics, L Nd.YAG laser, SP sample position.

Buker JF, Sample JD (1976) Tunable Diode Laser Instruments, ISA Reprint. Pittsburg, pp 76-613 Bulkin BJ (1976) Vibrational spectroscopy of liquid crystals. In Brown GH (ed) Advances in liquid crystals, vol 2. Academic, New York, p 199 Bulkin BJ (1981) Vibrational spectra of liquid crystals. In Clark RJH, Hester RE (eds) Advances in infrared and Raman spectroscopy, vol 8. Heyden, London, p 151 Bunker PR (1979) Molecular Symmetry and Spectroscopy. Academic Press, New York Bunow MR, Levin IW (1977a) Biochim Biophys Acta 464 202 Burch DE, Gryvnak DA (1967) J Chem Phys 47 4930... 

Hall RJ, Eckbreth A (1984) In Laser Applications, Ready F, Erf RK (eds). Academic, New York Hallam HE (ed) (1973) Vibrational Spectroscopy of Trapped Species. John Wiley, London Haller 1, Huggins HA, Lilienthal HR, McGuire TR (1973) J Phys Chem 77 950 Hamaguchi H (1985) In Advances in Infrared and Raman Spectroscopy, vol 12, Clark RJH, Hester... 

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