The application of Fourier transform Raman spectroscopy to the identification and characterization of polyamides—I. Single number nylons

High quality Fourier transform Raman spectra, free from fluorescence, have been obtained for a series of commercial polyamides of the single number nylon type from nylon 3 to nylon 12. With this newly developed technique, it is now possible to record spectra routinely and to characterize each nylon spectrum thus to identify them for analytical purposes. The characteristic trends observed in some regions of the Fourier transform Raman spectra obtained for this series of nylons are investigated and discussed.     

Applications of Fourier transform Raman spectroscopy in inorganic chemistry—a considered view

A sudy of a wide variety of coloured main group metal, transition metal coordination and transition metal organometallic complexes using Fourier transform Raman (FT-Raman) spectroscopy has demonstrated a high success rate (ca 50%) with good quality spectra obtained in short periods of time. It is suggested that FT-Raman spectroscopy should now be regarded as a routine spectroscopic tool for use in inorganic as well as organic research and teaching laboratories.     

Fourier transform Raman studies of materials and compounds of biological importance—II. The effect of moisture on the molecular structure of the alpha and beta anomers of d-glucose

The effects of small amounts of water added to the alpha and beta anomers of d-glucose have been investigated. The monohydrate of alpha-d-glucose was formed under these conditions and its FT-Raman spectrum has been recorded for the first time. The combination of crystallographic data and vibrational spectroscopy, based on the study of alpha and beta d-glucose, with special emphasis on conformation and configuration sensitive modes, enabled band assignments to be made for the monohydrate of alpha-d-glucose.     

The use of polarised Fourier transform Raman spectroscopy in morphological studies of uniaxially oriented PEEK fibres—some preliminary results

The use of Raman spectroscopy to measure crystallinity in uniaxially oriented poly(aryl ether ether ketone) (PEEK) fibres is discussed. It is shown that previously reported measurements based upon the 1608:1597 cm⁻¹ band intensity ratio are affected by molecular orientation, and as such their application to anisotropic samples must be regarded with caution. The use of the crystallinity-sensitive carbonyl bandhead frequency seems to be less sensitive to molecular orientation and so may be applicable to oriented samples—further work is required to calibrate this measurement with oriented samples of known crystallinity. Some preliminary data on the polarisation properties of the 1597 cm⁻¹ ring mode intensity in PEEK fibre bundles is also presented. These data suggest that the band displays perpendicular rather than parallel character with respect to the fibre long axes. Possible reasons for this effect are discussed. The Raman data indicate that molecular orientation is present in both melt-spun and drawn fibres. The spun fibres appear to be amorphous, but drawing induces significant crystallisation.     

Surface hydration of aqueous γ-Al2O3 studied by Fourier transform Raman and infrared spectroscopy—I. Initial results

The hydration of γ-Al₂O₃ has been studied by Fourier transform (FT) Raman and infrared (IR) spectroscopy, and by X-ray diffraction (XRD). The initial findings are presented, along with a discussion of the possible causes for the major spectral changes that occur after hydration. The aims of the study and ongoing research are described.     

The application of Fourier-transform Raman spectroscopy to the determination of conformation in poly(ε-caprolactam) chains

The Fourier-transform Raman spectra of various structural forms of poly(ε-caprolactam) have been obtained and the Raman bands characterizing planar and nonplanar conformation of the ε-caprolactam units have been defined. These bands have been used for the investigation of the conformational composition of ε-caprolactam sequences in several ε-caprolactam-butadiene block copolymers.     

High-resolution Fourier transform infrared spectroscopy and analysis of the ν12 fundamental band of ethylene-d4

The Fourier transform infrared (IR) spectrum of the ν₁₂ fundamental band of ethylene-d₄ (C₂D₄) has been measured with an unapodized resolution of 0.004 cm⁻¹ in the frequency range of 1030–1130 cm⁻¹. A total of 1340 assigned transitions have been analyzed and fitted using a Watson's A-reduced Hamiltonian in the I^r representation to derive rovibrational constants for the upper state (v₁₂=1) up to five quartic terms with a standard deviation of 0.00042 cm⁻¹. They represent the most accurate constants for the band thus far. The ground state rovibrational constants were also further improved by a fit of combination–differences from the IR measurements. The relatively unperturbed band was found to be basically A-type with a band centre at 1076.98492±0.00003 cm⁻¹.     

Gas chromatography—Fourier transform infrared spectroscopy—mass spectrometry. A powerful tool for component identification in complex organic mixtures

Fourier transform infrared spectrometry (FTIR) and mass spectrometry (MS) have been combined with gas chromatography (GC) for the identification of eluted components in a complex mixture. The combined technique, GC—FTIR—MS, provides simultaneous GC—FTIR and GC—MS data from a single injection.     

Fourier transform spectroscopy and direct potential fit of a shelflike state: application to E(4)1Σ(+) KCs

The paper presents high-resolution experimental study and a direct potential construction of a shelflike state E(4)(1)Σ(+) of the KCs molecule converging to K(4(2)S) + Cs(5(2)D) atomic limit; such data are of interest for selecting optical paths for producing and monitoring cold polar diatomics. The collisionally enhanced laser induced fluorescence (LIF) spectra corresponding to both spin-allowed E(4)(1)Σ(+) → X(1)(1)Σ(+) and spin-forbidden E(4)(1)Σ(+) → a(1)(3)Σ(+) transitions of KCs were recorded in visible region by Fourier transform spectrometer with resolution of 0.03 cm(-1). Overall about 1650 rovibronic term values of the E(4)(1)Σ(+) state of (39)K(133)Cs and (41)K(133)Cs isotopologues nonuniformly covering the energy range [16987, 18445] cm(-1) above the minimum of the ground X-state were determined with the uncertainty of 0.01 cm(-1). Experimental data field is limited by vibrational levels v' ∈ [2, 74] with rotational quantum numbers J' ∈ [1, 188]. The closed analytical form for potential energy curve (PEC) based on Chebyshev polynomial expansion (CPE) was implemented to a direct potential fit (DPF) of the experimental term values of the most abundant (39)K(133)Cs isotopologue. Besides analyticity, regularity, correct long-range behavior, and nice convergence properties, the CPE form demonstrated optimal balance on flexibility and constraint for the DPF of a shelflike state aggravated by a limited data set. The mass-invariant properties of the CPE PEC were tested by the prediction of rovibronic term values of the (41)K(133)Cs isotopomer which coincided with their experimental counterparts with standard deviation of 0.0048 cm(-1). The CPE modeling is compared with the highly flexible pointwise inverted perturbation approach model, as well as with conventional Dunham analysis of restricted data set v' ≤ 50. Reliability of the empirical PEC is additionally confirmed by good agreement between the calculated and experimental relative intensity distributions in the long E(v') → X(v") LIF progressions.     

Differentiating “hard” from “soft” woods using Fourier transform infrared and Fourier transform spectroscopy

The Fourier transform Raman and Fourier transform infrared spectra of six soft- and six hardwoods are presented in this paper. In contrast to conventional Raman spectroscope using visible excitation, the use of a near-infrared laser induced far less fluorescence, and this enabled high quality spectra to be obtained. It is shown that it is possible to differentiate between the two types of wood using both techniques, and the reasons for these differences are discussed.     

Illuminating the flesh of bone identification – An application of near infrared spectroscopy

Near infrared (NIR) reflectance spectroscopy coupled with chemometric analysis was evaluated as a non-destructive tool to discriminate skull bone samples from different animal species. In total 70 skull bones from animals of three classes (mammalians, avian and reptiles) were scanned in the wavelength range between 950 to 1650 nm. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used to analyse the NIR spectra of the skull samples. Correct classification rates of 96% and 81% were obtained for the classification of skull bone samples according to avian and mammalian classes, respectively. Overall, a 91% correct classification rate was obtained for the classification of skull samples according to the class (mammalian and avian). This study demonstrates the potential of NIR spectroscopy coupled with chemometric as data processing, as a means of a rapid, non-destructive classification technique for skull bone samples.     

Structural studies of gel phases—IV. An infrared reflectance and Fourier transform Raman study of silica and silica/titania gel glasses

Infrared reflectance and Fourier transform Raman spectroscopy have been used to study silica and silica/titania monoliths produced by the sol—gel route which had been subjected to a series of heat treatments. With increasing thermal treatment temperature, the gel—glass matrix is strengthed by bond shortening and a reduction in mean SiOSi bond angle and angular distribution for this feature. Results obtained at a range of temperatures were in good agreement to those obtained for vitreous silica. The incorporation of low levels (3% by weight) of titanium led to more disordered glasses which contain titanium in tetrahedral sites only. Evidence was obtained for the formation of SiOTi bonds, principally during the latter stages of densification at temperatures between 615 and 1000°C.     

High-resolution Fourier transform infrared absorption spectroscopy of the ν6 band of c-C3H2

The gas-phase high-resolution absorption spectrum of the ν(6) band of cyclopropenylidene (c-C(3)H(2)) has been observed using a Fourier transform infrared spectrometer for the first time. The molecule has been produced by microwave discharge in an allene (3.3 Pa) and Ar (4.0 Pa) mixture inside a side arm glass tube. The observed spectrum shows a pattern of c-type ro-vibrational transitions in which the Q-branch lines strongly and distinctly stand out in the spectrum. A combined least-squares analysis of the observed 216 ro-vibrational transitions together with 28 millimeter-wave rotational transitions from the previous study has resulted in an accurate determination of the molecular constants in the ν(6) state. The band center is found to be at 776.11622(13) cm(-1) with one standard deviation in parentheses, which is 2.3% lower than the matrix isolation value. The intensity ratio I(3)(ν(3))/I(6)(ν(6)) obtained from the observed ν(3) and ν(6) bands, 1.90(9), is somewhat lower than the ratio estimated from ab initio (2.4-2.6) and DFT (2.8) calculations.     

A Fourier transform Raman spectroscopic study of the structures of polyethylene composite films containing GaAs and GaAs〈Te〉

The structuring of initial and composite films based on the high-density polyethylene-containing semiconductor fillers GaAs and GaAs〈Te〉 is studied at room temperature via Fourier transform Raman spectroscopy. On the basis of changes in the intensities of Raman lines of skeletal and bending vibrations, strengthening of the crystalline structure of the composite films is investigated. The diffractograms of the samples are obtained, and their degrees of crystallinity are determined. It is shown that, depending on the type and concentration of the filler, the degrees of crystallinity of the composite films increase by a factor of 1.3–1.5 relative to that of the initial polyethylene. The results are explained within the three-phase model by changes in the supramolecular structure of the semicrystalline polymer.     

Structure of the hydration shell of 1,3-dimethyl-2-imidazolidinone according to FT—Raman spectroscopy

Russian Chemical Bulletin - The analysis of the shape of the ν(CO) vibrations of the isotropic Raman band for 1,3-dimethyl-2-imidazolidinone (1) in aqueous solutions and the calculations in...     

Evaluation of the application of attenuated total reflectance–Fourier transform infrared spectrometry (ATR–FTIR) and chemometrics to the determination of nutritional parameters of yogurt samples

A critical evaluation of the application of attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR) and partial least squares (PLS) to the determination of several nutritional parameters, such as the energetic value and the carbohydrate, protein and calcium contents, in commercially available yogurt samples was carried out. To this end, a highly heterogeneous population of 48 samples covering a wide range of yogurts obtained from the Spanish market was used. After correcting the spectra, hierarchical cluster analysis was performed in order to select a representative calibration set and the corresponding validation sample set. Different PLS models and several spectral windows were tested in order to evaluate their prediction capabilities for the validation set. For all nutritional parameters, with the exception of fat content, the procedure developed here provided good precision; the values obtained complied with the statutory values declared by the US FDA.     

Infrared and Raman studies of hydrogen bonded complexes involving acetone,acetophenone and benzophenone—II. Raman intensity of the vCO band

The effect of hydrogen bond formation on the Raman intensity of the v_CO band of acetone, acetophenone and benzophenone complexed with phenol derivatives (pK_a = 10.30-7.75) is investigated. The Raman intensity enhancement brought about by complex formation lies between 1.1 and 2.5 and is inversely related to the Raman intensity in the free base. Linear correlations are found between the square root of the intensity enhancement and the enthalpy of complex formation, the intercepts and the slopes depending on the nature of the proton acceptor. The depolarization ratio of the carbonyl band remains practically unchanged. The results are discussed in terms of σ and π electronic densities on the carbon and oxygen atoms of the carbonyl function.     

High resolution Fourier transform spectroscopy of the PbO molecule from investigation of the O2(1Δg)—Pb reaction

From the reaction of Pb with metastable oxygen O₂(¹Δ_g) in a Broida type oven we have analysed at high resolution some vibrational levels of the X0⁺, a1, A0⁺ and B1 states of the ²⁰⁸PbO molecule. The rotational parameters determined allowed us to recalculate the position of the various isotope lines to within 0.01 cm⁻¹. We have found a negative value of ω_eχ_e (−0.123 (25) cm⁻¹) in A0⁺, contrary to previous observations. The Ω type doubling in a1 varies from +1.8 × 10⁻⁴ cm⁻¹ (υ′ = 2) to +2.3 × 10⁻⁴ cm⁻¹ (υ′ = 9) and in B1 from −1.17 × 10⁻⁴ cm⁻¹ (υ′ = 0) to −0.97 × 10⁻⁴ cm⁻¹ (υ′ = 2).