Fourier transform raman spectroscopy using a bench-top fourier transform infrared spectrometer

The use of a bench top FTIR spectrometer for near infrared Fourier transform Raman spectroscopy is demonstrated. The use of near infrared excitation results in fluorescence free Raman spectra allowing previously difficult samples to be measured.     

Polarization fourier transform infrared spectroscopy

Some Fourier transform infrared spectroscopic studies with linearly and circularly polarized radiation are reported. They were all carried out by means of the differential technique, consisting in the comparison of two single-channel spectra of opposite polarization. Thus, linear dichroic or circular dichroic spectra with positive and negative bands were recorded. Typical application examples of both techniques are presented.     

Far infrared fourier transform spectroscopy of semiconductors

Fourier transform spectroscopy (FTS) is one of the most important tools in the study of shallow level donors and acceptors in semiconductors. When combined with a two-step photothermal ionization process detected photoconductively, FTS allows measurement of optical transitions of donor-bound electrons (and acceptor-bound holes) in ultra-pure germanium samples with impurity concentrations <10⁹ cm^–3 (i.e. one electrically active impurity in 4×10¹³ host atoms). The experimental high resolution study of the hydrogen-like excited state series of shallow levels has yielded as many as 19 lines of width as small as 10eV for some centers. These results have stimulated theoretical work which has led to the unambiguous assignment of quantum states to many bound excited states. Extensive studies of ultra-pure Ge crystals grown under different well-controlled conditions have led to the discovery of a large number of novel shallow impurity complexes. Study of the multiplicities and symmetries of the associated electronic states has led to a detailed understanding of the unusual static and dynamic structures of these novel centers. The chemical composition has been deduced from correlations between the concentration of a particular center and the materials involved in crystal gowth. Isotopic substitution of hydrogen with deuterium has led to the unambiguous proof of the presence of hydrogen in several of the novel centers. In addition to the high resolution spectra of shallow electronic levels, vibrational spectra of bond-centered interstitial oxygen in ultra-pure Ge are noteworthy for their extraordinarily sharp lines.     

The destruction-free analysis of polymers by fourier transform infrared photoacoustic and fourier transform Raman spectroscopy: A comparison

With the introduction of rapid–scanning Fourier transform infrared (FTIR) and recently Raman (FT–Raman) spectroscopy, vibrational spectroscopy has been launched into a new era of applications in polymer chemistry and physics. Thus, the increase in sensitivity provided by multiple scanning has led to the breakthrough of new, destruction–free sampling techniques, such as photoacoustic and Raman spectroscopy. This paper provides a comparison between data produced by FTIR photoacoustic and FT–Raman analysis of a range of polymers, and structural information available from both techniques is discussed.     

Frequency-sweep fourier transform ion cyclotron resonance spectroscopy

A single ion cyclotron resonance (ICR) absorption spectrum showing both CH⁺₃ and CH⁺₄ signals has been obtained by exciting both ion cyclotron resonances with a frequency-swept rf irradiation, followed by broad-band detection, digitization of the (time-domain) response, and finally discrete Fourier transformation to produce the (frequency-domain) spectrum. Pulsed-excitation Fourier transform ICR has demonstrated the use of broad-band detection in rapid generation of ICR spectra by Fourier transform methods; this paper demonstrates that frequency-sweep excitation can provide the broad-band irradiation required to excite ion cyclotron resonances throughout any desired mass range. It will thus be possible to obtain an ICR absorption spectrum of given mass range, signal-to-noise ratio, and resolution in an observation period which is two orders of magnitude shorter than that needed to obtain the same spectrum by conventional slow-sweep detection.     

Fourier transform raman spectroscopy of elastomers: An overview

The application of FF Raman spectroscopy in the field of elastomers has been reviewed. FT Raman spectra of various natural and synthetic elastomers are presented to illustrate both the advantages and the limitations of the technique.Carbon black and some oils, when compounded with natural and synthetic elastomers, prevent the acquisition of useful Raman spectra. However, all other commercial samples studied produced excellent spectra in the raw and vulcanized states without any sample pre-treatment.This has allowed quantitative work on blends and isomeric elastomers and also the direct study of the rubber vulcanization process.Future developments of the technique are discussed.     

Near infrared fourier transform Raman spectroscopy of human artery

We report the first near IR FT-Raman spectroscopy of normal diseased human artery. In normal human aorta, two bands at 1669 cm⁻¹ and 1452 cm⁻¹ dominate the spectrum and can be assigned to protein amide I and C-H in-plane bending vibrations, respectively. Weaker bands are also observed between 1250 and 1350 cm⁻¹. Non-calcified atherosclerotic lesions with a large amount of necrotic debris below the tissue surface show a relative increase in the intensity of the 1452 cm⁻¹ band. In atherosclerotic aortas which contain calcified deposits several hundred microns below the tissue surface, a strong 961 cm⁻¹ band is observed due to the symmetric stretch of phosphate groups in the calcified salts. The results show that this method provides the capability to probe biological substituents several hundred microns below the tissue surface.     

Application of fourier transform infrared spectroscopy to the study of semicrystalline polymers: Poly(ethylene terephthalate)

An infrared absorbance subtraction technique has been used to “isolate” bands in the composite spectrum of semicrystalline polymers according to their crystalline or amorphous character. Amorphous and crystalline spectra for annealed, melt-quenched, and solution-cast poly(ethylene terephthalate) have been separated. The spectra of the amorphous component show an increased intensity of bands associated with the trans configuration of oxygen about the C? C bond when the polymer is annealed. This increased “trans” band intensity reflects the increased proportion of trans structures as a result of annealing. The amorphous trans bands are shifted approximately 1–3 cm^?1 from their positions in the crystalline “trans” spectrum. The frequency shift of these bands can be attributed to the differences in chain interactions that exist in the amorphous phase and the crystalline lattice. We have also found that under identical anealing conditions the amorphous phase of the melt-quenched polymer contains an increased intensity of conformational trans bands compared to the sample cast from solution.     

Column switching applied to capillary gas chromatography/fourier transform infrared spectroscopy

A dual oven gas chromatograph incorporating a micro, mechanical switching valve has been interfaced to an FTIR spectrometer. With this system, each oven can be operated with independent temperature control. Complete choice of the columns' type and capacity gives flexibility in the separation prior to spectroscopic evaluation. An application which demonstrates some of the advantages of column switching in GC/FTIR is presented. Minor sample components have been successfully analyzed by heart-cutting the appropriate section of the separation from a high to a low capacity column. In this way, the dynamic range of the technique is effectively increased while an efficient chromatographic inlet to the FTIR is maintained.     

Mammalian cell growth studiedin situ by fourier transform infrared spectroscopy

Fourier transform infrared techniques were used to monitor mammalian cell growth plated on attenuated total reflection (ATR) crystals. Consistently, the growth kinetics plots generated from the obtained spectra demonstrated a sigmoidal curve representing a sequence of slow, rapid, then tapering cell growth which correlated well with non-spectral cell growth determinations. Significant advantages over traditional methods of measuring cell growth kinetics are demonstrated. The technique has promising potential to be used to study events in areas such as toxicology and cell biology.     

Biological applications of fourier transform infrared spectroscopy: a study of phase transitions in biomembranes

The thermal response of aqueous lipid membranes has been investigated by Fourier transform infrared spectroscopy. Changes in infrared spectral parameters are applied to the analysis of the strutural changes which occur within the lipid bilayer as the temperature is varied. Such studies provide the basis for the interpretation of phase transitions in complex biomembranes.     

A variable-temperature diffuse reflectance infrared fourier transform spectroscopy study of the binding of water and pyridine to the surface of acid-activated metakaolin

Four metakaolins were prepared by heating a Spanish kaolin at 600, 700, 800, and 900 degrees C for 10 h. Following preliminary optimization, these metakaolins were acid activated in 6 M hydrochloric acid at 90 degrees C for 6 h; the samples calcined at 600, 700, and 800 degrees C produced the highest surface area solids and were selected for further study. Variable-temperature diffuse reflectance infrared Fourier transform spectroscopy analysis of the resulting acid-activated metakaolins (AAMKs) identified a wide range of hydrogen bond strengths in adsorbed water at room temperature. Above 300 degrees C it was possible to fit the broad hydroxyl stretching band to seven contributing components at 3730, 3700, 3655, 3615, 3583, 3424, and 3325 cm(-1). As the sample temperature was increased, the 3730 cm(-1) band increased in intensity as the water hydrogen bonded to AlOHAl was thermally desorbed. The other six bands decreased in intensity. The spectra of adsorbed pyridine indicated the presence of both Br?nsted and Lewis acid sites on the surface of the air-dried AAMKs. Preheating the AAMK at 200 degrees C prior to pyridine sorption reduced the number of Br?nsted acid sites and increased the number of thermally stable Lewis acid sites. A reduction in the amount of adsorbed pyridine after pretreating the AAMK at 400 degrees C was tentatively attributed to a reduction in surface area. This was reflected in fewer thermally stable Lewis acid sites in the AAMK pretreated at 400 degrees C compared to the number present in the sample pretreated at 200 degrees C.     

涂石蜡大米傅立叶变换红外吸收光谱识别分析

针对11种未涂石蜡大米和18个涂不同量石蜡的大米样品,以石油醚提取的油脂为试样,采用傅立叶变换红外光谱仪,扫描样品的傅立叶变换红外吸收光谱,并对光谱进行预处理,提取红外特征信息,将2855与1746、1462与1163 cm-1处特征峰的面积比值为坐标,采用Origín 6.0软件作识别分类图.结果表明:特征峰的面积比值与所涂石蜡量成线性变化,大米油脂的特征峰面积比值在一定的区域分布,涂以0.05%以上石蜡的大米,其油脂特征峰面积比值与未涂石蜡米油脂的值有一定区别.     

Polychlorobiphenyls differentiation and identification by gas chromatography/fourier transform infrared spectroscopy

Reference infrared vapour phase spectra of 20 polychlorobiphenyls (PCBs) have been obtained by gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR). These spectra are consistent with those of PCB obtained by diffuse reflectance IR spectroscopy (DRIFT) and with those of more simple molecular structures (iodochlorobenzenes, 1-bromodichlorobenzenes). The IR frequencies of the GC/FTIR spectra of PCB are assigned in terms of substitution patterns. This work shows that GC/FTIR can be a good approach for differentiation and identification of PCB in complex mixtures.     

Combined thermogravimetry and fourier transform infrared spectroscopy techniques for gas evolution analysis

The usefulness of thermogravimetry has been amply demonstrated for a wide variety of material analysis applications. In many instances, however, additional information is required for adequate characterization of the sample and its thermal decomposition behaviour. In this respect, the analysis of evolved gases, or condensed liquids, has proven a highly useful approach. Among the various physical methods used for analysis of the thermal degradation products, infrared spectroscopy has often been found very powerful, being versatile, rapid and widely accessible. In this study, we report a simple new approach in which the evolved gases and condensed liquids from the thermal decomposition of various products are recuperated in an infrared gas cell and on a PVC membrane filter, respectively. The gaseous components were analysed by transmission FT-IR, and the condensed liquid products were examined directly on the PVC membrane by FT-IR in the internal reflexion mode. The technique was used, for example, to examine the pyrolysis products (gases and liquid) of Koberit, a proposed substitute for asbestos. The method was also applied to the study of chemically derivatized asbestos materials in an attempt to unravel the surface chemical modifications.     

Phosphorus-containing podands. 8. A study of metal-ligand interaction by fourier transform infrared spectroscopy in anhydrous acetonitrile

The interaction of phosphorus-containing monopodands with Li⁺, Na⁺, and K⁺ cations in anhydrous CH₃CN has been studied by FTIR spectroscopy. It has been shown that phosphoryl groups of the ligands take part in the formation of complexes with the alkali metal cation. The IR results obtained do not permit a clear conclusion as to whether or not the ether oxygen atoms of the ligand polyether chain participate in the complexation. It is suggested that in CH ₃ CN the formation of 1:1 complexes is not accompanied by conformational reorganization of the monopodand.Institute of Physiologically Active Substances, Russian Academy of Sciences, Chernogolovka 142432. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 884–889, April, 1992.     

A study of wet PVC gels by raman spectroscopy

Raman spectroscopy has been used to study PVC gels made in cyclohexanone in the wet state at concentrations from 21 to 93% by weight of PVC. Parallel and perpendicular spectra were obtained in the C-Cl stretching region, and after subtraction of the solvent spectrum they were analyzed into a set of overlapping peaks due to various structural components. The positions of the peaks found were in good agreement with those found earlier for PVC samples in the solid state. The fractional contribution of the areas of peaks assigned to crystalline material to the total area under the C-Cl stretching region was used to estimate the crystallinity of the gels, and changes in their depolarization ratios and relative intensities were interpretated as providing further evidence for the presence of two types of crystallites in PVC gels. From a determination of the crystallinity at the gel transition point and reasonable assumptions, the contributions of the two types of crystallites to the total crystallinity were estimated.     

In-situ measurement of photochemical changes of solid samples by fourier transform infrared photoacoustic spectroscopy

Infrared spectral changes of lithographic printing plates were measuredin-situ by PAS and RAS. The advantages of PAS over RAS were discussed for the spectral measurements of organic coatings on roughened metal surface.