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.     

Study of the ν2 + ν3 infrared band of ONCl

Two hundred and sixty A type rovibrational lines of the ν₂ + ν₃ vibrational band of ¹⁶O¹⁴N³⁵Cl, around 925 cm⁻¹, have been assigned; a least-squares calculation with a r.m.s. deviation of 0.0006 cm⁻¹ has made it possible to measure several constants of the (011) vibrational level.     

High-resolution Fourier-transform infrared spectroscopy of the ν6 and Coriolis perturbation allowed ν10 modes of ketenimine

High-resolution FTIR spectra of the short lived species ketenimine have been recorded in the region 700-1300 cm(-1) and over 1500 transitions of the ν(10) and ν(6) modes have been assigned. Effective rotational and centrifugal distortion parameters for the v(10) = 1 and v(6) = 1 (excluding K(a) = 5) states were determined by co-fitting transitions, and treating strong a- and c-axis Coriolis interactions between them. Other perturbations attributed to interactions with the v(8) = 2 and v(12) = 1 + v(8) = 1 dark-states were also observed and treated. The ν(10) transitions are predicted to be inherently very weak, but are enhanced by an intensity stealing effect with the highly IR active ν(6) mode. A mechanism for this intensity stealing in ketenimine is also detailed.     

Determination of α-amylase activity using Fourier transform infrared spectroscopy

A new method for the determination of -amylase activity in aqueous solutions and human serum with FTIR-spectroscopy is proposed. The chemical reaction catalyzed by the enzyme under study can be followed directly when applying FTIR-spectroscopic detection also in the case, where no colored or electrochemical active species are generated or consumed during the course of the reaction of -amylase with simple starch. Therefore the determination of the -amylase activity could successfully be performed by recording two FTIR-spectra, one immediately after mixing the sample and a substrate (starch-) solution and the other after a 20 min reaction time. From these two FTIR-spectra a difference spectrum was calculated hereby eliminating an unspecific absorption of the matrix. The intensities of the resulting difference spectra corresponded to the extent of the reaction which took place during the investigated time interval and hence could be related to the activity of the enzyme in the sample. The developed method is linear from 80 to 1400 U/l (r.s.d.=5% for 700 U/l) in aqueous solutions and was also successfully applied to the determination of -amylase activity in human serum where a linear working range from 100 to 800 U/l (r.s.d.=11% for 150 U/l) was achieved.     

High-resolution Fourier-transform infrared spectroscopy of the Coriolis coupled ground state and ν7 mode of ketenimine

High resolution FTIR spectra of the short lived species ketenimine have been recorded in the regions 390-1300 cm(-1) and 20-110 cm(-1) using synchrotron radiation. Two thousand six hundred sixty transitions of the ν(7) band centered at 693 cm(-1) and 126 far-IR rotational transitions have been assigned. Rotational and centrifugal distortion parameters for the ν(7) mode were determined and local Fermi and b-axis Coriolis interactions with 2ν(12) are treated. A further refinement of the ground state, ν(12) and ν(8) parameters was also achieved, including the treatment of previously unrecognized ac-axis and ab-axis second order perturbations to the ground state.     

Fourier transform infrared isotopic study of ZnC3: identification of the ν1(a') mode

An isomer of ZnC(3) with bent structure in its (1)A(') electronic state has been detected in the products from the dual laser ablation of carbon and zinc rods that were trapped in solid Ar at ~12 K. Measurements of (13)C isotopic shifts have enabled the identification of the ν(1)(a(')) asymmetric carbon stretching fundamental at 1858.9 cm(-1). The experimental results are in good agreement with the predictions of DFT-B3LYP/6-311G(d) calculations that indicate a singlet bent isomer ground state structure with triplet linear and singlet cyclic isomers lying slightly higher in energy. This is the first optical detection of any isomer of ZnC(3).     

Fourier transform infrared isotopic study of linear MnC3: identification of the ν1(σ) fundamental

Linear MnC(3) has been detected in the products from the dual laser ablation of carbon and manganese rods trapped in solid Ar at ～12 K. The ν(1)(σ) vibrational fundamental, an asymmetric carbon stretching mode, has been identified at 1846.9 cm(-1). Fourier transform infrared measurements of (13)C isotopic shift are in good agreement with the predictions of density functional theory calculations using the mPW1PW91 functional with 6-311+G(3df) basis set. This is the first optical detection of the linear isomer of MnC(3) for which previous photoelectron spectroscopy studies have reported evidence of a cyclic isomer.     

Infrared diode laser spectroscopy of the ν2(2+ ← 1−) band of H3O+

Rotational lines in the ν₂ = 2⁺ ← 1⁻ “hot” band of the inversion mode of the oxonium (H₃O⁺) ion have been recorded by diode laser absorption spectroscopy. The ion was generated in low pressure gas discharges and detected using both velocity modulation and modulated hollow cathode techniques. Analysis of the spectra using a simple oblate symmetric top model has allowed the rotational parameters describing the 2⁺ inversion state to be determined for the first time. The band origin lies at 521.4383(52) cm⁻¹. These data will be useful in refining the oxonium ion inversion potential function and should aid in the analysis of other bands involving or perturbed by the 2⁺ level.     

Profile analysis of infrared absorption of NH stretching band

The shape of the infrared NH stretching band of N-methyl aniline in different solvents has been studied. Carbon tetrachloride, tetrachloroethylene, carbon disulfide, benzene, anisole, chloroform, dioxane and di-n-butyl ether were used as solvents. Band shapes observed show self-association of N-methyl aniline in dioxane, di-n-butyl ether and chloroform solutions.Moments analysis and time autocorrelation function calculations have been performed. The frequencies of the band maximum are more sensible to the solvent than the half band width and the band shape. Moments values depend strongly on the integration interval. The correlation function shows non-exponential decays in a short time range (0–0.16 ps) for any solutions, and this indicates that the molecular motions do not obey a simple rotational diffusion model. Exponential decays show at times longer than 0.16 ps. Relaxation times are linearly related with the solvents viscosity.     

Study of the ν1, ν1 + ν3 and ν2 + ν3 infrared bands of ONCl

A type (ΔK_a = 0) rovibrational lines of the near-prolate asymmetric top ¹⁶O¹⁴N³⁵Cl have been assigned on high resolution Fourier transform spectra: 820 lines of the ν₁ band, centered around 1800 cm⁻¹, 435 lines of the ν₁ + ν₃ band, centered around 2131 cm⁻¹, and 257 lines of the ν₂ + ν₃ band, centered around 925 cm⁻¹. Least-squares calculations have been carried out over these lines, using the A reduced Watson's hamiltonian in I^r representation; r.m.s. standard deviations of 0.0016 cm⁻¹, 0.0016 cm⁻¹ and 0.006 cm⁻¹ have been respectively obtained, making it possible to measure molecular constants of the (001), (101) and (011) vibrational levels of ¹⁶O¹⁴N³⁵Cl.     

Note: Deperturbation of the ν3 band of BeD2

High rotational levels of the 001 (Σ(u)) state of BeD(2) are perturbed by the nearby 03(3)0 (Φ(u)) state. Deperturbation analysis results in an experimental value for the vibrational energy of the 030 level.     

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.     

High-resolution FTIR spectroscopy of the ν8 and Coriolis perturbation allowed ν12 bands of ketenimine

High resolution FTIR spectra have been recorded in the region 250-770 cm(-1) using synchrotron radiation and over 2000 transitions to the ν(8) and ν(12) states of the short lived species ketenimine have been assigned. Ground state combination differences combined with published microwave transitions were used to refine the constants for the ground vibrational state. Rotational and centrifugal distortion parameters for the v(8) = 1 and v(12) = 1 levels were determined by co-fitting transitions, and treating a strong a-axis Coriolis interaction. Selection rules for the observed ν(12) transitions indicate that they arise solely from "perturbation allowed" intensity resulting from this Coriolis interaction.     

Water adsorption on tin hydrodioxide and its effect on the contour of the infrared absorption band ν(OH)

Tin hydrodioxide SnO₂ · nH₂O (THO, n = 1.5) pellets in potassium bromide were studied by IR absorption spectroscopy. Water adsorption by tin hydrodioxide was shown to give rise to a prominent strong and broad band of stretching vibrations ν(OH) with a peak at 3430 cm^?1. Absorption intensity of this band decreases with distance from the peak rapidly toward higher frequencies and very slowly toward lower frequencies; therefore, the contour is distinguished by very high asymmetry. Analysis of the reasons for this asymmetry taking into account the computer decomposition of the contour into components implies that the unresolved bands from two types of water molecules in THO are superimposed onto the weak bands from two types of hydroxide groups. First type molecules are involved in physisorption to form, with one another, hydrogen bonds that are similar to weak bonds in zeolite and liquid water. Second type molecules are involved in chemisorption and are coordinated to tin ions. Coordination enhances the strengthening of acidic properties and promotes the appearance of strong H-bonds. The peak intensity of the THO ν(OH) band depends primarily on the contribution of vibrational transitions of first type molecules and to a lesser extent on the contribution of vibrational transitions of the first type hydroxide groups. The vibrational transitions in second type molecules and second type groups influence the curvature of the contour on the low-frequency side of the peak.     

Fourier transform infrared studies of 5′-GMP in 2H2O and H2O solutions.

In a previous work (ref. 1) we observed important changes in the 1700–1400 cm⁻¹ region of FTIR spectra in ²H₂O solutions when 5′-GMP concentration increases. These changes can be attributed to the self-association of this mononucleotide. Recently, study of this process has been extended to other regions of the spectrum and to H₂O solution. Fourier deconvolution has been employed in order to resolve the broad band into component bands. Differences have been observed between spectra in H₂O and ²H₂O for the same solute concentration. The possible causes of these differences are indicated.     

Characterization of ABA block copolymers polystyrene-poly(γ-benzyl-l-glutamate) by Fourier transform infrared spectroscopy

The composition of ABA block copolymers polystyrene-poly(γ-benzyl-l-glutamate) was determined by Fourier transform infrared spectroscopy. This could be achieved by establishing a calibration curve of the integrated intensity of the NH stretching band of α-helical poly(γ-benzyl-l-glutamate) between 3137 and 3550 cm⁻¹ as a function of concentration. There is a fairly good agreement between the composition values obtained by FTIR and those obtained by elemental nitrogen analysis.     

Molecular dynamics simulations for CO(2) absorption spectra. I. Line broadening and the far wing of the ν(3) infrared band

Classical molecular dynamics simulations (CMDS) have been carried out for gaseous CO(2) starting from the intermolecular potential energy surface. Through calculations for a large number of molecules treated as rigid rotors, various autocorrelation functions (ACFs) are obtained together with probabilities of rotational changes. Those used in the present paper are the ACFs of the center of mass velocity and of the molecular orientation, and the conditional probability of a change of the angular speed. They enable calculations, respectively, of the mass diffusion coefficient, of the infrared (dipolar) band shape including the wings, and of individual line-broadening coefficients. It is shown that these calculations, free of any adjustable parameter, lead to good agreement with measured values. This is expected from previous studies for the mass diffusion coefficient and line-broadening coefficients, but it is, to our knowledge, the first demonstration of the interest of CMDS for the prediction of band wings. The present results thus open promising perspectives for the theoretical treatment of the difficult problem of far wings profiles.     

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.