OH Bending Research Articles

Phonon-assisted proton tunneling in the hydrogen-bonded dimeric selenates of Cs3H(SeO4)2.

In phases III and IV of Cs3H(SeO4)2, the vibrational state and intrabond transfer of the proton in the dimeric selenates are systematically studied with a wide range of absorbance spectra, a spin-lattice relaxation rate of 1H-NMR (T1 -1), and DFT calculations. The OH stretching vibrations have extremely broad absorption at around 2350 (B band) and 3050 cm-1 (A band), which originate from the 0-1 and 0-2 transitions in the asymmetric double minimum potential, respectively. The anharmonic-coupling calculation makes clear that the A band couples not only to the libration but also to the OH bending band. The vibrational state (nano-second order) is observed as the response of the proton basically localized in either of the two equivalent sites. The intrabond transfer between those sites (pico-second order) yields the protonic fluctuation reflected in T1 -1. Together with the anomalous absorption [νp2 phonon, libration, tetrahedral deformation (δ440), and 610-cm-1 band], we have demonstrated that the intrabond transfer above 70 K is dominated by the thermal hopping that is collectively excited at 610 cm-1 and the phonon-assisted proton tunneling (PAPT) relevant to the tetrahedral deformation [PAPT(def)]. Below 70 K, T1 -1 is largely enhanced toward the antiferroelectric ordering and the distinct splitting emerges in the libration, which dynamically modulates the O(2)-O'(2) distance of the dimer. The PAPT(lib) associated with the libration is confirmed to be a driving force of the AF ordering.

Inter- and Intramolecular Vibrational Energy Flow in a Formamide-Water Complex.

The role of hydrogen bonds in energy redistribution in the cyclic structure of a formamide-water complex has been studied with semiclassical formulations of energy transfer probabilities and solutions of the equations of motion. We show high efficiency of near-resonant vibrational energy from initially excited OH stretching to the first overtone of the bending vibration, which is followed by ultrafast (∼100 fs) energy redistribution in the accepting modes of the complex. A strong coupling of the OH bending vibration with the low-frequency modes generated in the hydrogen-bonding intermolecular regions, especially that formed between the water oxygen and formamide hydrogen, plays the key role of ultrafast relaxation of the overtone mode, transferring energy to the hydrogen bonds and distant functional groups in the complex.

Vibrational Energy Transfer in a Water Chain

Vibrational energy transfer through hydrogen bonding in water chains is a fast and efficient process. The chain consisting of 10 water molecules and a ground‐state nitric oxide at the end is collisionally excited by another nitric oxide molecule with an excess vibrational energy corresponding to in the v = 1 state from the other end, where the energy transfer proceeds through the hydrogen bonds. Energy transfer from the impact site to the end of chain occurs in a picosecond time scale, taking a subpicosecond over single hydrogen bond. The energy transfer pathway is a sequence of the initial OH‐stretching excitation on the impact to the OH bending overtone mode and then to the bound nitric oxide through a series of low‐frequency intermolecular vibrational states. More than 80% of the initial OH‐stretching excitation passes through the hydrogen bonds and deposits in the bound nitric oxide at the end of the chain. In the majority of trajectories, energy passing through the N…H bond at the terminal site leads to its subsequent bond rupture, thus producing a vibrationally excited nitric oxide in the region remote from the initial impact site.

A fast and reliable 2D-IR spectroscopic technique for herbal leaves classification

The safety and quality of herbal products are of great importance. People take herbal products with the intention for health improvement and overall well-being. Both chromatographic and spectroscopic techniques have been proven for their effectiveness in phytochemical fingerprinting and profiling. The present study describes the application of advanced two dimensional correlation infrared spectroscopy (2D-IR), and followed by chemometrics for herbal leaves classification. The 2D-IR could ascertain small difference and reveal for any overlapping peaks compared to conventional FTIR technique. There were 13 herbs selected and their dried leaves in fine powder form were used for spectral scanning from 400 to 4000 cm−1. The absorption signals were analysed by principal component analysis (PCA) and hierarchical clustering analysis (HCA). It was found that the wavenumber of 1800–900 cm−1 was the dominant region of identification and discrimination. The region was found to have signals attributed to the functional groups of CO, CO and CC stretching, and CH and OH bending. Both PCA and HCA could cluster the IR spectral data of the herbs into 4 distinct groups. There was no significant relationship of leaf morphology and phytoconstituents similarity. Somehow, hairy (Strobilanthes crispa and Morus alba) and waxy (Eurycoma longifolia and Citrus hystrix) leaf surfaces of the herbs are still grouped together after data extraction and reduction using the pattern recognition tools. The classification was also verified by introducing another 3 new spectral data (S. crispa, M. alba and Ficus deltoidea) into the statistical analysis. The new dataset was found to be located at the position near to their individual plant species in both score plot and dendrogram. Although the absorption signals of the new dataset were obtained from their aqueous crude extract, 2D-IR spectroscopic analysis was still capable to capture the key features of discrimination for classification in a precise and rapid manner.

Jet-cooled rovibrational spectroscopy of methoxyphenols using two complementary FTIR and QCL based spectrometers.

Methoxyphenols (MPs) are a significant component of biomass burning emissions which mainly exists in our atmosphere in the gas phase where they contribute to the formation of secondary organic aerosols (SOAs). Rovibrational spectroscopy is a promising tool to monitor atmospheric MPs and infer their role in SOA formation. In this study, we bring a new perspective on the rovibrational analysis of MP isomers by taking advantage of two complementary devices combining jet-cooled environments and absorption spectroscopy: the Jet-AILES and the SPIRALES setups. Based on Q-branch frequency positions measured in the Jet-AILES Fourier-transform infrared (FTIR) spectra and guided by quantum chemistry calculations, we propose an extended vibrational and conformational analysis of the different MP isomers in their fingerprint region. Some modes such as far-IR out-of-plane -OH bending or mid-IR in-plane -CH bending allow us to assign individually all the stable conformers. Finally, using the SPIRALES setup with three different external cavity quantum cascade laser sources centered on the 930-990 cm-1 and the 1580-1690 cm-1 ranges, it was possible to proceed to the rovibrational analysis of the ν18 ring in-plane bending mode of the MP meta isomer providing a set of reliable excited state parameters, which confirms the correct assignment of two conformers. Interestingly, the observation of broad Q-branches without visible P- and R-branches in the region of the C-C ring stretching bands was interpreted as being probably due to a vibrational perturbation. These results highlight the complementarity of broadband FTIR and narrowband laser spectroscopic techniques to reveal the vibrational conformational signatures of atmospheric compounds over a large infrared spectral range.

UV-irradiated gelatin-chitosan bio-based composite film, physiochemical features and release properties for packaging applications

In this study, Chitosan-Gelatin biodegradable films loaded with Gallic acid (GA) were developed. Ethanol, tween, and β-Cyclodextrin (β-CD) were used to enhance the distribution of GA in the film forming solutions. The effect of the exposure time of UV irradiation on the color, mechanical properties (TS, %E), water vapor permeability (WVP) microstructure and release rate of GA to fatty food simulants investigated. UV irradiation reduced darkness of the films markedly and increased the release rate of the GA. Among the non-irradiated samples the highest and lowest release rate were obtained for the films containing β-CD and ethanol respectively. On the other hand incorporation of β-CD could reduce the increasing effect of UV light on release rate. The UV irradiation for 10 min reduced mechanical strength and barrier properties of the film against water vapor. Microscopic analysis, showed the consistent and uniform microstructure. However, long-term radiation caused some cracks in the films network. The UV irradiation weakened the _OH bending and enhanced the amide I amide II.

IR observation of activated ether species on acidic OH groups on H-ZSM-5 zeolites

IR spectra of ethers adsorbed on zeolite (H-ZSM-5) were analyzed in detail in comparison with those of water and alcohols. Interpretation of complicated features of IR spectra observed for adsorption of water and alcohols on acidic OH groups of zeolite is summarized in relation with the adsorption structure and the potential energy based on the accepted knowledge. Since the presence of Fermi resonance in vibrational modes between acidic OH groups and adsorbed species can be an estimate for the potential energy of the protonated transition state, IR spectra of adsorption of ethers on zeolite were interpreted by changing acidic OH groups to OD. Adsorption of ethers on silanol and acidic OH groups of zeolite resulted in markedly different IR spectra. In addition, the Fermi resonance between OH stretching of acidic OH (shifted below 2000 cm−1) and CH bending vibrations of adsorbed ethers was confirmed, and the observed adsorbed species were co-existent with protonated transition state in equilibrium at 298 K.

Estimation of elemental composition of agricultural soils from West Azerbaijan, Iran, using mid-infrared spectral models

ABSTRACT Characterizing the elemental composition provides useful information about the weathering degree of soils. In Miandoab County, Northern Iran, this characterization was missing, and thus the objectives of this work were to evaluate the weathering degrees for the most typical soils in the area from their elemental compositions, and to estimate this elemental composition using Fourier transform infrared spectroscopy and Random Forest models. Five soil profiles, including Aridisols and Inceptisols, were selected as the most representative of the area. Major elemental oxides were determined in each genetic horizon by X-ray fluorescence, showing that these soils were at early developmental stages. Only Al2O3 and CaO were accurately estimated, with R2 values of 0.8, and out-of-bag mean square errors of 0.2 and 1.1, respectively. The other oxides were not predicted satisfactorily, probably due to small differences in their elemental compositions. Random Forest provided the important spectral bands related to the content of each element. For Al2O3, these bands were between 500 and 650 cm-1, which represent out-of-plane OH bending vibrations and Al-O gibbsite and alumino-silicate vibrations. For CaO, the most important bands are related to carbonate content. A combination of Fourier transform infrared spectra and Random Forest models can be used as a rapid and low-cost technique to estimate the elemental composition of arid and semi-arid soils of Northern Iran.

Effect of NH4H2PO4 content on properties of P-Sn-W-B glass system with ultra-low melting sealing temperature

The glass structure, thermal and electrical properties and water durability of the P-Sn-W-B glasses, prepared by traditional melt-quenching technique, were examined. The glasses exhibited relatively low transition temperatures (90–150 °C), ultra low sealing temperature (250–300 °C), high electrical resistivity (ρv = 1011–13 Ω·cm), high coefficient of thermal expansion(CTE = 182–230*10−7/K), and excellent water durability, could be used as low melting sealing material. With the increasing NH4H2PO4/P2O5 ratio, the O/P ratio increased, from the EDX analysis. The glass structure changed with the composition, the infrared spectra showed that the PO double bonds, OH bending vibration decreased whereas new bonds like P-O-W formed, enhancing the glass structure, also, the water durability of glass was improved.

Terrestrial humic-like fluorescence peak of chromophoric dissolved organic matter as a new potential indicator tracing the antibiotics in typical polluted watershed

Natural surface waters are threatened globally by antibiotics pollution. In this study, we analyzed antibiotics and CDOM (Chromophoric dissolved organic matter) fluorescence in different water bodies using HPLC method and Excitation Emission Matrix- Parallel factor analysis, respectively. A combination of field studies in the Yinma River Watershed were conducted in rivers, reservoirs and urban rivers, and 65 CDOM and antibiotic samples were taken in April, May, July, and August 2016. EEM-PARAFAC analysis identified two components; a humic-like (C1) component and a tryptophan-like (C2) component. The redundancy analysis (RDA) demonstrated that CDOM could explain 38.2% (two axes) of the five antibiotics in reservoirs (N = 31), and 26.0% (two axes) of those in rivers and urban water (N = 30). Furthermore, the Pearson correlation coefficient between Sulfamethoxazole and C1 in reservoir water was 0.91 (t-test, 2-tailed, p < 0.01), and that between Sulfamethoxazole and C2 was 0.68 (t-test, 2-tailed, p < 0.01). This indicated that the humic-like component of CDOM PARAFAC fluorescence could detect Sulfamethoxazole contamination levels in the homogenized reservoir waters. Our results identified Sulfamethoxazole and Quinolones (Norfloxacin, 16.5 ng L−1; Enrofloxacin, 0.3 ng L−1; Ciprofloxacin, 30.9 ng L−1) at mean concentrations of 369.5 ng L−1 and 15.9 ng L−1, respectively, which were the higher levels in natural surface waters. The FTIR spectroscopy of the mixture of humic acid and sulfamethoxazole showed that the absorbance at 3415 cm−1 linked to OH stretching of OH groups and at 1386 cm−1 because of OH bending and vibration of COOH groups became weaker, indicating that COOH groups of humic acid can adsorb and react with –NH2 of sulfamethoxazole. The CDOM PARAFAC components can be adapted for online or in situ fluorescence measurements as an early warning of Sulfamethoxazole distribution and contamination in similar aquatic environments.

Vanadium oxide (V2O3) for energy storage applications through hydrothermal route

V2O3 samples were successfully prepared using [VOSO4·xH2O] as the starting material by a template-free hydrothermal method with the addition of KBrO3. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV). The XRD result shows the rhombohedral structure for V2O3 with an average crystallite size in the range of 22 nm. With the increase in reaction time (6–8 h), the morphology of the samples changes from nano-flower to nano-ribbons as indicated by SEM micrographs. FTIR spectrum shows that the band at 1286 cm−1, related to C–OH stretching and OH bending vibrations and indicate the presence of residual hydroxyl groups. The electrochemical measurements show an excellent storage response, kinetics and reversibility of the electrode material. Further, good rate capability of the materials was also observed.

XRD and ATR/FTIR investigations of various montmorillonite clays modified by monocationic and dicationic imidazolium ionic liquids

Three different montmorillonites (Mts) labeled K10, KSF and SWy-3 were analyzed by X-ray diffraction and ATR/FTIR spectroscopy. The XRD results enabled validation of the purification process of the studied clays. In the spectral regions 3800–2600 and 1800-1300 cm-1, the study of different intensity ratios of peaks assigned to the OH bending and stretching modes displayed the specific vibrational behavior of SWy-3 which is certainly influenced by a greater proportion of Na+ in its structure. Before analyzing the clays modified by ionic liquids, we characterized two imidazolium based ionic liquids (ILs) with anion I-: [EMIM+] [I−] monocationic ionic liquid and [M(CH₂) IM2+] [2I−] dicationic ionic liquid. The passage from [EMIM+] [I−] to [M(CH₂) IM2+] [2I−] reveals significant vibrational changes through various modes: ν(NH), rings ν(CC), rings ν(CN), ν(CH2(N)), ν(CH3(N)) in addition to anion interaction modes. When purified, these ionic liquids modify clays, the XRD analysis shows that the studied modified clays exhibited higher d-value increase with respect to the purified Mts, and the reflection peaks 2θ (°) of plane (001) were displaced towards lower values as a consequence of the ionic liquid intercalation process. ATR/FTIR spectra recorded in the spectral zone 4000-600 cm-1 indicated the appearance of new peaks and a significant intensity variation between clays in relation to the type of chosen ionic liquid. These vibrational changes are directly connected to the presence of ionic liquids in clays. XRD and ATR/FTIR investigations show a stronger effect of the [M(CH2) IM2+] [2I−] dicationic ionic liquid on the Mts than the monocationic ionic liquid and the SWy-3 Mt is more sensitive to monocationic and dicationic ionic liquids than K10 and KSF Mts.

Biosorption of Cr(VI) from wastewater using Sorghastrum Nutans L. Nash

ABSTRACTSorghastrum Nutans L. Nash is used as an adsorbent for the removal of Cr(VI) from wastewater. Adsorption coupled reduction i.e. indirect reduction is the mechanism of Cr(VI) removal by the biomaterial. The adsorbent surface became highly positively charged at lower pH, adsorption rate of Cr(VI) is faster and reduction reaction also accelerates at lower pH since the binding of negatively charged Cr(VI) ion species to the cationic groups is enhanced and protons take part in this reaction. The adsorbent is characterised by using XRD, FTIR, SEM and EDAX analysis. OH bending, CN stretching/bending and NH stretching play a major role in Chromium adsorption. Experimental values follow pseudo-second order reaction and Langmuir adsorption isotherm. Surface diffusion is the rate controlling mechanism for the process. The maximum percentage of Cr(VI) removal obtained is 75.5% with 7 g/L dosage at pH 1.3 and adsorbate concentration was 100 mg/L. From the normal probability, residual, contour, 3D surface, main effect and interaction plot along with t-test, ANOVA, and F-test, it is observed that pH has the most significant effect on the percentage removal followed by adsorbent dosage and time. The adsorbate concentration has the least effects and interaction effects are found to be significant.

Vibrational tug-of-war: The pKA dependence of the broad vibrational features of strongly hydrogen-bonded carboxylic acids.

Medium and strong hydrogen bonds give rise to broad vibrational features frequently spanning several hundred wavenumbers and oftentimes exhibiting unusual substructures. These broad vibrational features can be modeled from first principles, in a reduced dimensional calculation, that adiabatically separates low-frequency modes, which modulate the hydrogen bond length, from high-frequency OH stretch and bend modes that contribute to the vibrational structure. Previously this method was used to investigate the origin of an unusual vibrational feature frequently found in the spectra of dimers between carboxylic acids and nitrogen-containing aromatic bases that spans over 900 cm-1 and contains two broad peaks. It was found that the width of this feature largely originates from low-frequency modes modulating the hydrogen bond length and that the structure results from Fermi resonance interactions. In this report, we examine how these features change with the relative acid and base strength of the components as reflected by their aqueous pKA values. Dimers with large pKA differences are found to have features that can extend to frequencies below 1000 cm-1. The relationships between mean OH/NH frequency, aqueous pKA, and O-N distance are examined in order to obtain a more rigorous understanding of the origin and shape of the vibrational features. The mean OH/NH frequencies are found to correlate well with O-N distances. The lowest OH stretch frequencies are found in dimer geometries with O-N distances between 2.5 and 2.6 Å. At larger O-N distances, the hydrogen bonding interaction is not as strong, resulting in higher OH stretch frequencies. When the O-N distance is smaller than 2.5 Å, the limited space between the O and N determines the OH stretch frequency, which gives rise to frequencies that decrease with O-N distances. These two effects place a lower limit on the OH stretch frequency which is calculated to be near 700 cm-1. Understanding how the vibrational features of strongly hydrogen-bonded structures depend on the relative pKA and other structural parameters will guide studies of biological structures and analysis of proton transfer studies using photoacids.

Direct Vibrational Energy Transfer in Monomeric Water Probed with Ultrafast Two Dimensional Infrared Spectroscopy

Vibrational relaxation dynamics of monomeric water molecule dissolved in d-chloroform solution were revisited using the two dimensional Infrared (2D IR) spectroscopy. The vibrational lifetime of OH bending in monomeric water shows a bi-exponential decay. The fast component (T1=(1.2±0.1) ps) is caused by the rapid population equilibration between the vibrational modes of the monomeric water molecule. The slow component (T2=(26.4±0.2) ps) is mainly caused by the vibrational population decay of OH bending mode. The reorientation of the OH bending in monomeric water is determined with a time constant of τ=(1.2±0.1) ps which is much faster than the rotational dynamics of water molecules in the bulk solution. Furthermore, we are able to reveal the direct vibrational energy transfer from OH stretching to OH bending in monomeric water dissolved in d-chloroform for the first time. The vibrational coupling and relative orientation of transition dipole moment between OH bending and stretching that effect their intra-molecular vibrational energy transfer rates are discussed in detail.

Computational and Experimental Study of Thermodynamics of the Reaction of Titania and Water at High Temperatures

Gaseous titanium hydroxide and oxyhydroxide species were studied with quantum chemical methods. The results are used in conjunction with an experimental transpiration study of titanium dioxide (TiO2) in water vapor-containing environments at elevated temperatures to provide a thermodynamic description of the Ti(OH)4(g) and TiO(OH)2(g) species. The geometry and harmonic vibrational frequencies of these species were computed using the coupled-cluster singles and doubles method with a perturbative correction for connected triple substitutions [CCSD(T)]. For the OH bending and rotation, the B3LYP density functional theory was used to compute corrections to the harmonic approximations. These results were combined to determine the enthalpy of formation. Experimentally, the transpiration method was used with water contents from 0 to 76 mol % in oxygen or argon carrier gases for 20-250 h exposure times at 1473-1673 K. Results indicate that oxygen is not a key contributor to volatilization, and the primary reaction for volatilization in this temperature range is TiO2(s) + H2O(g) = TiO(OH)2(g). Data were analyzed with both the second and third law methods using the thermal functions derived from the theoretical calculations. The third law enthalpy of formation at 298.15 K for TiO(OH)2(g) at 298 K was -838.9 ± 6.5 kJ/mol, which compares favorably to the theoretical calculation of -838.7 ± 25 kJ/mol. We recommend the experimentally derived third law enthalpy of formation at 298.15 K for TiO(OH)2, the computed entropy of 320.67 J/mol·K, and the computed heat capacity [149.192 + (-0.02539)T + (8.28697 × 10-6)T2 + (-15614.05)/T + (-5.2182 × 10-11)/T2] J/mol-K, where T is the temperature in K.

Synthesis and characterization of magnetic activated carbon developed from palm kernel shells

Magnetic activated carbon (MG-AC), a solid product made by dispersing magnetic substrates on AC, is gaining attention for the removal of heavy metals from wastewater due to its favorable physico-chemical properties such as enhanced surface area and magnetic properties, respectively. However, the effects of two contrasting substrates, i.e., metal solution and metal particles, for the synthesis of MG-AC to obtain enhanced magnetic property have not been considered. The MG-AC was prepared by incorporating Fe3O4 into the AC from two different sources of iron: Fe3O4 extracted from electric arc furnace slag and from a ferric chloride/ferrous sulfate solution, to produce magnetic palm kernel shell from slag (MG-PKSS) and magnetic palm kernel shell from iron suspension (MG-PKSF), respectively. The adsorbent samples were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-ray diffraction, electron microscopy, i.e., SEM and FESEM, energy-dispersive X-ray, nitrogen adsorption, vibrating sample magnetometer. The results showed that the MG-PKSF had a greater BET surface area of 257 m2 g−1, a pore volume of 0.1124 cc g−1 and higher magnetic properties with a magnetic saturation of 49.55 emu g−1 relative to the MG-PKSS. The FTIR spectrum of the MG-PKSF illustrated the intense OH bending at 1629 cm−1 which can be attributed to the presence of oxygen in the samples. The absorption bands at 1093 and 579 cm−1 indicated the presence of C–O stretching and metal–oxygen (M–O) bands due to the interaction of iron and oxygen. Therefore, the MG-PKSF presented better characteristics for heavy metal removal from wastewater relative to the MG-PKSS, thereby suggesting that the raw material (metal solution) for impregnation played a crucial role in enhancing the quality of the MG-AC.

Sulfate decontamination from groundwater by metal layered double hydroxides functionalized high phosphorus iron ore waste as a new green adsorbent: Experimental and modeling

The reuse of mine wastes is an efficient method to reduce disadvantages of the mining operation. High phosphorous iron ore (HPI) waste as a common waste of iron mine has been modified by Ni-Al and Ni-Fe hydroxide metals and utilized as a sulfate adsorbent. These adsorbents were characterized by XRD, XRF, FTIR, SEM, BET and TGA analyses. According to characterization studies, by loading Metal Layered Double Hydroxides (Ni-Al and Ni-Fe hydroxide metals) onto HPI Ore Waste appropriate adsorptive spaces and pores were emerged on the surface of Ni-Fe and Ni-Al HPI which were shown by enhancement intensity of OH bending vibrations in FTIR analysis, increase of Loss On Ignition (L.O.I) value in XRF analysis and the thermal stability reduction in TGA. The RSM method based on central composite design (CCD) was used to investigate the optimum condition. The amount of adsorption in optimum condition led to 34 and 29.89mg/g for Ni-Al and Ni-Fe HPI, respectively. The equilibrium studies have been carried out by the consideration of Langmuir, Freundlich, Temkin, D-R, Redlich-Peterson, Khan, and Koble–Corrigan isotherm models, which displayed that sulfate adsorption onto both adsorbents were performed favorably and chemically. Sulfate adsorption on to Ni-Al and Ni-Fe HPI occurred by the homogenous and heterogeneous process, respectively. Kinetic studies were performed by applying pseudo-first-order, pseudo-second-order and Boyd models which indicated the chemisorption interaction for all three adsorbents by a controlling step of the film diffusion. The adsorption process was modeled by the extended geometric method by an acceptable estimation fitted well with experimental data. Thermodynamic studies indicate that sulfate adsorption process onto Ni-Al and Ni-Fe HPI were exothermic and associative.

Effect of a Waterproofing Agent on the Penetration Process of Water into a Cellulose Acetate Film by Time-resolved Coherent Anti-Stokes Raman Scattering (CARS) Microspectroscopy

The penetration of water into a cellulose acetate (CA) film with m-terphenyl (m-TP) as a waterproofing agent (WPA) was investigated in real time by coherent anti-Stokes Raman scattering (CARS) microspectroscopy. Owing to the WPA, the water penetration was significantly suppressed. It was manifested by a small spectral change in comparison with the CA films without m-TP. Moreover, the amplitude of the Raman band at 1600 cm−1 due to the OH bending mode, which is the marker band of water penetration, was significantly smaller. The present results indicate that m-TP has significant effects as a WPA for CA films on the water penetration process.

Ab initio study of fast small-amplitude vibrations as functions of slow large-amplitude motions in CD3OH and comparison to CH3OH

Ab initio quantum chemical calculations generating a two-dimensional map of the energy surface and vibrational frequencies have been carried out for CD3OH and CH3OH over ranges of the torsional angle γ and the OH bend angle ρ. We have explored the frequency variation of the fast small-amplitude asymmetric ν2 and ν9 CD and CH stretching modes of E parentage as functions of the slow large-amplitude γ and ρ coordinates associated with the torsional and OH-bending modes that would form a degenerate e pair in the ρ=0° limit of COH linearity. The Gaussian09 program package was employed to calculate minimized energies, structures and Hessians on a grid of points with γ varying from 120° to 180° from the top to the bottom of the torsional potential barrier and ρ varying from 0° at linearity up to a 100° bend. The energies, average frequencies and frequency differences for each species have been fitted to a model combining Fourier expansions in the torsional angle with power-series in the OH-bend angle (Thapaliya et al., 2015) and the expansion constants are presented and compared for the two isotopologues. The conical intersection points of degeneracy between the ν2 and ν9 frequencies have been located for CD3OH, close to those known for CH3OH (Dawadi and Perry, 2014). For CD3OH, CD stretching frequencies calculated along the IRC torsional path from top to bottom of the barrier have been fitted to a high-order local mode model for comparison with earlier results for CH3OH (Xu, 2000), and A-E torsional splittings have been predicted for the three CD stretches.