Fourier transform infrared emission spectra of MgH and MgD

High resolution Fourier transform infrared emission spectra of MgH and MgD have been recorded. The molecules were generated in an emission source that combines an electrical discharge with a high temperature furnace. Several vibration-rotation bands were observed for all six isotopomers in the X (2)Sigma(+) ground electronic state: v=1-->0 to 4-->3 for (24)MgH, v=1-->0 to 3-->2 for (25)MgH and (26)MgH, v=1-->0 to 5-->4 for (24)MgD, v=1-->0 to 4-->3 for (25)MgD and (26)MgD. The new data were combined with the previous ground state data, obtained from diode laser vibration-rotation measurements and pure rotation spectra, and spectroscopic constants were determined for the v=0 to 4 levels of (24)MgH and the v=0 to 5 levels of (24)MgD. In addition, Dunham constants and Born-Oppenheimer breakdown correction parameters were obtained in a combined fit of the six isotopomers. The equilibrium vibrational constants (omega(e)) for (24)MgH and (24)MgD were found to be 1492.776(7) cm(-1) and 1077.298(5) cm(-1), respectively, while the equilibrium rotational constants (B(e)) are 5.825 523(8) cm(-1) and 3.034 344(4) cm(-1). The associated equilibrium bond distances (r(e)) were determined to be 1.729 721(1) A for (24)MgH and 1.729 157(1) A for (24)MgD.     

Fourier transform Raman and infrared and surface-enhanced Raman spectra for rhodamine 6G

The vibrational spectra of rhodamine 6G (R6G) are discussed on the basis of Fourier transform infrared and Fourier transform Raman spectra obtained far from resonance which are compared with resonance Raman and surface-enhanced resonance Raman spectra obtained with excitation at 457.9 nm. The behaviour of several bands is described and tentative assignments are proposed. Stong resonance Raman effects are observed for bands assignable to xanthene ring stretching modes and also xanthene ring deformation modes. Some of these are sensitive to the complexing of R6G with silver colloids.     

Fourier transform infrared spectra and molecular structure of 5-methoxytryptamine,N-acetyl-5-methoxytryptamine and N-phenylsulfonamide-5-methoxytryptamine

5-Methoxytryptamine (5-MT) is a potent antioxidant and has radioprotective action. N-acetyl-5-methoxytryptamine (melatonin, NA-5-MT) is a free radical scavenger and antioxidant, which protects against oxidative damage due to a variety of toxicants. The infrared spectra of 5-MT, NA-5-MT and new synthesized N-phenylsulfonamide-5-methoxytryptamine (PS-5-MT) were investigated in the region between 4000 and 400 cm(-1). Vibrational assignments of the molecules have been made for fundamental modes on the basis of the group vibrational concept, infrared intensity and comparison with the assignments for related molecules. X-ray powder diffraction patterns of molecules were also recorded. In order to optimize the geometries of the molecules, molecular mechanic calculations (MM3) were performed. Conformational analysis of 5-MT, NA-5-MT and PS-5-MT was also established by the using PM3 method.     

Attenuated total reflection Fourier transform infrared spectra of faceted diamonds

In this work, the contributions of cationic and elemental gold on roughened gold substrates to surface-enhanced Raman scattering (SERS) of polypyrrole (PPy) films were first investigated. First, a gold substrate was roughened by a triangular wave oxidation-reduction cycle (ORC) in an aqueous solution containing 0.1 M KCl. Then, the roughened gold substrate was further reduced by applying a cathodic potential for a fixed time to control the quantity of unreduced cationic Au on the roughened Au substrate. The result indicates that the content of cationic Au is responsible for the improved SERS of PPy electrodeposited on this roughened Au substrate. This phenomenon can be attributed to the interfacial charge transfer from PPy to the roughened Au substrate by the aid of cationic Au.     

Fourier transform infrared and Raman spectra of N-di-isopropylphosphorylguanidine (DPG)

The Fourier transform infrared and the Fourier transform Raman spectra of N-di-isopropylphosphorylguanidine (DPG) in the solid state and in aqueous solution were recorded and analyzed. Assuming Cs symmetry for different structural fragment of the molecule, the experimental and calculated band assignments of the nu(NH), delta(HNH), delta(CNH), nu(C=N), nu(PN), nu(CN), nu(PO) and nu(OC) normal modes suggested that the DPG exists as a tautomeric contribution of the phosphorylamine (I) and N-phosphorylimine (II) structural forms. [structures: see text]     

Time-resolved Fourier transform infrared emission spectroscopy of laser ablation products

Time-resolved Fourier transform infrared spectroscopy was applied for observations of emission spectra from ablation products induced by a Nd:YLF laser with a 2.5 kHz repletion rate. The infrared emission spectra from Fe, Cu, Zn, and Al atoms were observed in the 2.5–5 μm region. The observed emission spectrum from iron ablation in the 2500 cm⁻¹ region agrees very well with solar absorption spectrum, where new lines have been detected in the present experiment in addition to the lines observed from a hollow cathode discharge. When O₂ was added to the carbon ablation, emissions from vibrationally excited CO were observed with non-equilibrium vibrational distribution.     

Low-temperature Fourier transform infrared spectra and hydrogen bonding in polycrystalline L-alanine

The 400-4000 cm(-1) FTIR spectra of pure NH and isotopically substituted (10 and 90% doped ND/NH) polycrystalline L-alanine were recorded in the temperature range 10-300 K. The observed temperature dependence and isotopic shifts behavior enabled to identify, in the spectra of the doped crystals, three well-separated bands ascribable to either the NH or ND stretching vibrations associated with the three different types of hydrogen bonds existing in the crystal. The observed red shifts of these bands relative to the frequency of a reference "free" NH (or ND) stretching mode were found to correlate well with the H-bond distances found in the crystal and provide an indirect way of estimating the enthalpies associated with each type of H-bond found in the crystal. In the low-frequency deformation and torsional spectral region (below 2000 cm(-1)), several bands, which were found to be affected by isotopic substitution, were identified as belonging to the NH3(+) group. Several bands show splitting at low temperatures, indicating the occurrence of a significant reorganization in the crystal structure, which with all probability results mainly from changes in the proton positions. Finally, the literature assignments of the IR spectra of both crystalline NH3(+) and ND3(+) L-alanine were revised taking into consideration their temperature dependence and behavior upon deuteration.     

ICP argon emission in the near infrared 1–2μm by high resolution Fourier transform spectrometry

The emission characteristics of the inductively coupled plasma in the near infrared spectral region from 0.9 to 2.0μm have been recorded by high resolution Fourier transform spectrometry. This region contains many strong atomic argon lines. The 109 lines with signal-to-noise ratio greater than four in the observed spectrum are identified and reported here with wavenumber accuracy on the order of 0.001 cm^?1. Also reported are relative intensities and line widths. This information is useful for determining spectral interferences to be expected in the development of analytical applications for the ICP in the near infrared.     

Structural analysis and Fourier transform infrared and Raman spectra of dibutoxyphosphoryl benzylisothiourea

A structural analysis for dibutoxyphosphoryl benzylisothiourea (DBBT) was carried out by mass spectrometry, 1H NMR, 13C NMR, infrared and Raman spectroscopy. The Fourier transform infrared and Fourier transform Raman spectra of liquid of DBBT were carried out with the purpose of studying the tautomerism (structures I and II) and the behavior of the more polar absorption's bands in different solvents, i.e., absorption's of the P=O and C=N bands. The results suggest the existence of tautomerism in the pure (liquid) compound and in solution of CHCl(3), CH(2)Cl(2), CHBr(3), and THF, C(2)H(4)Cl(2) and C(2)H(4)Br(2). The solvent interaction with the P=O band was characterized by the presence of a new band in the region of the O-H absorption. A vibrational assignment of the IR bands and Raman shifts was done and is proposed in this paper.     

Fourier transform infrared spectra and micelle formation of sodiumn-alkanesulfonates in aqueous solution

The concentration dependences of the Fourier transform infrared spectra of aqueous solutions of sodiumn-pentanesulfonate,n-hexanesulfonate,n-heptanesulfonate, andn-octanesulfonate were studied in concentration ranges encompassing the critical micellization concentrations (c.m.c). Changes in wavenumber, bandwidth, and intensity of infrared absorption bands were used to monitor the changes in molecular association with concentration. The premicellar aggregation below the c.m.c. may accompany the association of the alkyl chain, but not the counter-ion binding with the SO ₃ ^– group. Above the c.m.c, the front location of the counter-ion against the SO ₃ ^– group at the micelle surface is demonstrated.     

The effect of apodization and finite resolution on Fourier transform Raman spectra

The effects that finite resolution and choice of apodization function have on Fourier transform (FT) Raman spectra are illustrated by the 839 cm⁻¹ (ν₁) and 914 cm⁻¹ bands of KMnO₄. FT-Raman spectra were recorded at 0.5, 1, 2, 4, 8, 16 and 32 cm⁻¹ resolution using boxcar, Norton—Beer (strong, medium and weak) and triangular apodization functions at each resolution. The results show the dramatic changes in bandshape that occur as the ratio (resolution/true full width at half height of band) increases. The changes were measured in terms of the full width at half height of the band, the height of the band, the area of the band and the bandshape (expressed as a sum of Lorentzian and Gaussian lines). At a given resolution the degree to which each of these characteristics is affected is strongly dependent on the choice of the apodization function.     

Fourier transform infrared and Raman spectral investigations of 5-aminoindole

Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectra of 5-aminoindole has been recorded and analysed. The FT-IR spectrum of the compound was recorded in a BrukerIFS 66 V spectrometer in the range 4000-400 cm(-1) and the FT-Raman spectrum was also recorded in the same instrument in the region 3500-100 cm(-1). Observed frequencies for normal modes are compared with those calculated form normal co-ordinate analysis. The shift in the frequencies of the fundamental modes with the substituent amino group and the mixing of different normal modes are discussed with the help of potential energy distribution (PED) calculated through normal co-ordinate analysis.     

Density functional theory study of Fourier transform infrared and Raman spectra of 2-amino-5-chloro benzonitrile

The vibrational spectra of 2-amino-5-chloro benzonitrile (ACB) have been obtained by density functional theory (DFT) calculations. Normal coordinate analysis has been carried out to support the vibrational analysis. The results were compared with the experimental values. With the help of scaling procedures, the observed FTIR and FT Raman vibrational frequencies were analysed and compared with the theoretically predicted vibrational spectra. The assignments of bands to various normal modes of the molecules were also carried out.     

正交信号校正用于傅里叶变换红外光谱的模型传递

近红外轻质油品快速检测技术的研制与应用,替代了实验室轻质油品的传统检验,实现检验业务批量自动进样、快速检测、自动清洗、机器代人和无人值守,解决了传统检测效率低、工作量大、成本高的问题. 同时也改善了有毒有害人工检测环境,及时准确的提供产品的质量信息,指导装置优化调整生产工艺参数,有效促进资源的合理利用和生产工艺优化提升,满足企业生产装置精细化管理和优化运行的需求,带动行业内轻质油品快速检测技术的创新发展.     

A study of the near infrared emission bands of the hydroperoxyl radical at medium resolution

Emissions of the hydroperoxyl radical HO₂ in the spectral range from 1.0 to 1.6 μm were studied at low and medium resolution. The resolved spectrum shows the expected parallel band structure for the vibrational ovetone transition ²A″ (200-000); in the case of the vibronic transitions ²A′, 000 → ²A″, 000 and ²A′, 001 → ²A″, 000, however, comparison of experimental and computer simulated spectra shows that there also occur intense subbands with ΔK = 0, in addition to the ordinary ΔK = ± 1 transitions. The cause for the break-down of the type-C selection rule is not well known. In the reaction system of ethylene with discharged oxygen vibronic bands could be observed originating from ²A′ levels up to at least ν′₃ = 6. The most probable excitation mechanism for these high vibronic levels is the chemiluminescent reaction HCO + O₂ (¹Δ_g) → HO₂(²A′, 00ν′₂) + CO. From the computer fits to the spectra of HO₂ and DO₂ at medium resolution the origins of the 000-000 bands and the fundamental frequencies $\text{ν}$_3′ of the excited ²A′ state could be determined; the values are $\text{ν}$_o(HO₂)=7028 ± 3 cm^?1, $\text{ν}$_o(DO₂)=7034 ± 8 cm^?, $\text{ν}$_3′(HO₂)=927 ± 10 cm^?, and $\text{ν}$_3′(DO₂)=940 ± 28 cm^?1.     

High resolution infrared spectra and rovibrational analysis of the coupled nu2/nu5 bands of D3Si35Cl. Equilibrium rotational constants

The Fourier transform infrared spectrum of monoisotopic D3Si35Cl in the region of the nu2/nu5 band system was recorded with a resolution of 2.4x10(-3) cm-1. More than 9000 lines of the strongly Coriolis x,y-coupled bands, (nu2)0=701.936, and (nu5)0=688.898 cm-1, have been assigned, among them 276 forbidden but perturbation allowed transitions around avoided crossings according to Delta(k-l)=+/-3 mechanisms. Three different models taking into account redundancies in the framework of unitary equivalent reductions of the rovibrational Hamiltonian have been employed to fit the data. All three models reproduced consistently the full data set employing 28 refined parameters with an rms deviation of 0.31x10(-3) cm-1. The equivalence of the parameter sets was established by the agreement of parameter sums obtained with the different models. The analysis of the avoided crossings, together with the fit of the forbidden lines, allowed an independent determination of the ground state parameters A0 and D(K)0. Combined with existing data for nu1, nu3, nu4, and nu6, the present results allowed the determination of experimental values, Ae=1.4371895(94) and Be=0.19823049(59) cm-1. The experimental results are compared with those of previous ab initio calculations of the anharmonic force field.     

Proton hydration in aqueous solution: Fourier transform infrared studies of HDO spectra

This paper attempts to elucidate the number and nature of the hydration spheres around the proton in an aqueous solution. This phenomenon was studied in aqueous solutions of selected acids by means of Fourier transform infrared spectroscopy of semiheavy water (HDO), isotopically diluted in H(2)O. The quantitative version of difference spectrum procedure was applied for the first time to investigate such systems. It allowed removal of bulk water contribution and separation of the spectra of solute-affected HDO. The obtained spectral data were confronted with ab initio calculated structures of small gas-phase and polarizable continuum model (PCM) solvated aqueous clusters, H+(H2O)n, n=2-8, in order to help in establishing the structural and energetic states of the consecutive hydration spheres of the hydrated proton. This was achieved by comparison of the calculated optimal geometries with the interatomic distances derived from HDO band positions. The structure of proton hydration shells outside the first hydration sphere essentially follows the model structure of other hydrated cations, previously revealed by affected HDO spectra. The first hydration sphere complex in diluted aqueous solutions was identified as an asymmetric variant of the regular Zundel cation [The Hydrogen Bond: Recent Developments in Theory and Experiments, edited by P. Schuster, G. Zundel, and C. Sandorfy (North-Holland, Amsterdam, 1976), Vol. II, p. 683], intermediate between the ideal Zundel and Eigen structures [E. Wicke et al., Z. Phys. Chem. Neue Folge 1, 340 (1954)]. Evidence was found for the existence of strong and short hydrogen bonds, with oxygen-oxygen distance derived from the experimental affected spectra equal 2.435 A on average and in the PCM calculations about 2.41-2.44 A. It was also evidenced for the first time that the proton possesses four well-defined hydration spheres, which were characterized in terms of hydrogen bonds' lengths and arrangements. Additionally, an outer hydration layer, shared with the anion, as well as loosely bound water molecules interacting with free electron pairs of the central complex were detected in the affected spectra.     

Low temperature Fourier transform infrared spectra and hydrogen bonding in polycrystalline uracil and thymine

The FTIR spectra of pure NH and isotopically diluted (NH/ND and ND/NH) polycrystalline uracil and thymine were measured in the range 4000-400 cm(-1) at temperatures from 300 to 10K. For the first time, the essentially narrow bands corresponding to the uncoupled stretching (nu(1)) and out of plane bending (nu(4)) NH proton modes of uracil and thymine were observed in the solid phase. It was found that in the nu(4) region the spectra reveal more details on the H-bond interactions present in both solids than in the nu(1) range. The frequencies of the various bands observed in both spectral regions were used for estimation of the H-bond energy, using empirical correlations between this property and both the red shift of nu(1) and the blue shift of nu(4) that occur upon crystallization due to the establishment of the H-bonds. The results are compared with known thermodynamic, structural and theoretical data. The IR data also suggest that the H-bond networks of both crystals contain, besides the two NH...O=C bonds revealed by X-ray experiments, additional types of H-bonds, which do not show long range periodicity and, thus, cannot be detected by the conventional structural methods. The assignment of some other bands in the spectra of both substances was also reviewed.     

Fourier transform-based deconvolution techniques for resolution of overlapping bands in x-ray photoelectron and fourier-transform infrared spectra of bisphenol-a-polycarbonate/dimethyl siloxane block copolymers

A series of bisphenol-A-polycarbonate/poly(dimethylsiloxane) (BPAC/DMS) block copolymers is studied by x-ray photoelectron (x.p.s.) and Fourier-transform infrared (F.t.i.r.) spectroscopies. Previous quantitative results, obtained without resolution enhancement, provided calibration of the signal-processing techniques used. A Van Cittert technique for x.p.s. is evaluated for the deconvolution of the carbon 1s core photoelectron spectrum, and self-deconvolution by Fourier methods is evaluated for the overlapping Si-CH₃ and aromatic C—O stretch bands at 1261 and 1228 cm^-1, respectively, in the i.r. spectrum. These features can be utilized in quantitative analysis of the surface and bulk of the BPAC/DMS copolymers. The ability of deconvolution techniques to narrow the bands artificially so as to resolve complex spectral envelopes, while retaining the quantitative data is discussed. The studies illustrate the ability of modern signal processing techniques to extract exact complex data from spectroscopic results, and allow quantitative evaluation without standards for complex polymer systems.