Vibrations Of Molecules Research Articles

Theoretical study on direction of vibrational transition dipole moment of XH stretching vibration in HXD

Experimental vibrational spectra of heavy light XH stretching vibrations of simple molecules have been analyzed using the local mode model. In addition, the bond dipole approach, which assumes that the transition dipole moment (TDM) of the XH stretching mode is aligned along the XH bond, has helped analyze experimental spectra. We performed theoretical calculations of the XH stretching vibrations of HOD, HND−, HCD, HSD, HPD−, and HSiD using local mode model and multi-dimensional normal modes. We found that consistent with previous notions, a localized 1D picture to treat the XH stretching vibration is valid even for analyzing the TDM tilt angle. In addition, while the TDM of the OH stretching fundamental transition tilted away from the OH bond in the direction away from the OD bond, that for the XH stretching fundamental of HSD, HND−, HPD−, HCD, and HSiD tilted away from the OH bond but toward the OD bond. This shows that bond dipole approximation may not be a good approximation for the present systems and that the heavy atom X can affect the transition dipole moment direction. The variation of the dipole moment was analyzed using the atoms-in-molecule method.

Об ангармонических колебаниях двухатомной молекулы и атомарного димера

According to modern concepts, the interaction potential as a function of the interatomic distance has a single minimum, has no other extremum points, and does not have inflection points, where its derivative is zero. Usually, to take into account harmonic vibrations and the effect of anharmonic effects on these vibrations, the interaction potential is expanded in the Taylor series and a quadratic term is taken into account, which takes into account harmonic vibrations, and third and fourth order corrections for deviations of the interatomic distance from its equilibrium value, taking into account anharmonic effects. These three members of the Taylor series constitute an approximate interaction potential. To take into account the anharmonic effects in the partition function of the diatomic molecule in the Boltzmann factor, an exponential factor is selected that takes into account the anharmonic part of the above approximate potential, and this factor is expanded in the Taylor series, the integration limits are changed to plus and minus infinity, the integration is carried out and the first few members of the power series are left on return temperature. Obviously, the approximate potential, like the initial potential, should not have other extremum points, except for a single minimum, and inflection points, where its derivative is equal to zero. In this paper, it is shown that: if the coefficient in front of the fourth-order term in the approximate potential is negative, then the approximate potential has two false maxima; if it is zero, then there is one false maximum; if it is positive, then the potential can have one false minimum and one false maximum or one inflection point where the derivative of the potential is equal to zero. The conditions imposed on the interaction potential are found when the anharmonic effects in the vibrations of a diatomic molecule can be approximately taken into account by corrections of the third and fourth orders to the quadratic harmonic potential. It is shown that this approximation can be used in the case of the interaction of atoms of a diatomic molecule by means of the Mie-Grüneisen and Lennard-Jones potential.

Terahertz Spectroscopy for Characterization of Hydrogen Bonding and Cross-linked Structure Dynamics in Polyurethane

Terahertz (THz) absorption spectra of cross-linked polyurethane films were observed at 30–180 °C. The obtained spectra displayed characteristic absorption bands. A band observed at 2.6 THz was assigned to the C=O···N-H hydrogen bond vibration using previously reported data. DFT calculation results confirmed that a band at 7.5 THz arises owing to the torsional vibration of cross-linked molecules containing urethane bonds. The slight changes in the temperature-dependent spectra were analyzed by the first derivative of absorption intensity with temperature. The thermal behavior of absorption intensities indicates the dynamics of hydrogen bonds and cross-linked structures in polyurethane films.

Synthesis of nanostructured silica/hydroxyapatite hybrid particles containing amphiphilic triblock copolymer for effectively controlling hydration layer structures with cytocompatibility.

We synthesized nanostructured mesoporous silica (MS)/hydroxyapatite (HA) hybrid particles in the presence of amphiphilic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO20PPO70PEO20) triblock copolymer (P123). The particles exhibited slit-shaped mesostructures and underwent hybridization reaction between the MS and HA phases containing P123. Furthermore, the aggregated form of the particles exhibited dispersion stability in water in the monodispersed state (average particle size: 145 nm and coefficient of variation: 4.3% in the case of the maximum added amount of P123). Then, the structures of the hydration layer and the adsorbed protein on the particles were investigated to understand the effect of the hydration layer structures on the protein secondary structures. The ratio of the bonding water (intermediate and nonfreezing water) to free water increased upon hybridization, and it decreased with increasing P123 concentration. Upon hybridization, the component ratio of the asymmetric O-H stretching vibration between free water molecules decreased, and that of the symmetric O-H stretching vibration of intermediate water molecules increased. With increasing P123 concentration, the asymmetric O-H stretching vibration between free water molecules increased and the symmetric O-H stretching vibration of intermediate water molecules decreased. It was found that the protein native state component ratios of α-helix and β-sheet increased with increasing symmetric O-H stretching vibration between intermediate water molecules, and they decreased with decreasing asymmetric O-H stretching vibration between free water molecules. Moreover, the cytotoxicity against osteoblasts (MC3T3-E1) was evaluated and the hybrid particles exhibited a high cell density, indicating their bioactivity. On the hybrid particles interacting with P123, the cells were three-dimensionally assembled and uniaxially grown with the culture. Therefore, this is the first successful report of the synthesis of nanostructured MS/HA hybrid particles interacting with P123, and the controlled hydration layer structures on the particle surfaces were found to contribute to the protein secondary structures, promoting cytocompatibility.

Nonstationary CARS by Polaritons

One of the significant problems of molecular spectroscopy is the determination and detailed analysis of how molecular vibrations are dephased. The dephasing of infrared-active (IR-active) vibrations of molecules was investigated by IR absorption spectroscopy. Pulse methods were used to investigate IR-vibrations as well. These methods revealed such coherent nonstationary effects as optical nutation, damping of the free polarization, photon echo, etc. New means of studying dephasing processes were uncovered by the method of nonstationary (time-domain) coherent anti-Stokes Raman scattering (CARS) spectroscopy. However, there are some aspects of CARS that still are not fully covered. One of them is related to Raman scattering by polaritons in dipole-active crystals whereas the second one is the increase of efficiency of CARS (minimization of the wave mismatch, the relationship between pulse width and the relaxation time, etc.). The purpose of the present research to study the case of “extreme” coherency between all interacting pulses (the duration of each pulse is smaller than characteristic times and those pulses are traveling with the same speed) in dipole-active crystals. In this research, we analyzed the process of simultaneous propagation of three waves (anti-Stokes, Stokes, and the pump) under CARS by polaritons. We have found some solutions modeling such simultaneous propagation. We also found the expression for the gain factor for such scattering. The gain factor was evaluated under the assumption of a given stationary pump field. It was shown that the typical values of the relative intensities were consistent with the experimental results.

Structure and Spectral Characteristics of Glucose

Compared with the traditional methods, the fully random conformational search based on Monte Carlo is more random and comprehensive. In this paper, the structural characteristics and spectral vibration of glucose molecules are studied by this method, and the results are compared with the existing results, which are highly consistent in all aspects, confirming the scientificity and accuracy of this method. At last, the properties, functions and spectral vibrations of glucose are studied by combining electrostatic analysis and spectral analysis. This method provides a new way to study the related properties of other biomolecules.

Raman Imaging of Plant Cell Walls.

Raman imaging is a microspectroscopic approach revealing the chemistry and structure of plant cell walls in situ on the micro- and nanoscale. The method is based on the Raman effect (inelastic scattering) that takes place when monochromatic laser light interacts with matter. The scattered light conveys a change in energy that is inherent of the involved molecule vibrations. The Raman spectra are thus characteristic for the chemical structure of the molecules and can be recorded spatially ordered with a lateral resolution of about 300nm. Based on thousands of acquired Raman spectra, images can be assessed using univariate as well as multivariate data analysis approaches. One advantage compared to staining or labeling techniques is that not only one image is obtained as a result but different components and characteristics can be displayed in several images. Furthermore, as every pixel corresponds to a Raman spectrum, which is a kind of "molecular fingerprint," the imaging results should always be evaluated and further details revealed by analysis (e.g., band assignment) of extracted spectra. In this chapter, the basic theoretical background of the technique and instrumentation are described together with sample preparation requirements and tips for high-quality plant tissue sections and successful Raman measurements. Typical Raman spectra of the different plant cell wall components are shown as well as an exemplified analysis of Raman data acquired on the model plant Arabidopsis. Important preprocessing methods of the spectra are included as well as single component image generation (univariate) and spectral unmixing by means of multivariate approaches (e.g., vertex component analysis).

Lattice vibrations of the molecular crystal of photoreactive substance with defects

Lattice vibrations are studied theoretically by density-functional based tight-binding methods for the model structure of 2-(2'-hydroxyphenyl)benzoxazole crystal with defects. 2-(2'-hydroxyphenyl)benzoxazole is a photoreactive compound that exhibits excited state intramolecular proton transfer in the structure with an OH...N hydrogen bond. The unit cell of the model structure consists of two crystal unit cells where the molecules have the structure with intramolecular hydrogen bonds OH...N and one molecule is supposed to have a different orientation of the whole molecule or its fragment. The different orientation of the fragment forms the structure with an intramolecular hydrogen bond OH...O. It is calculated that defect caused by the different orientation of the molecule have a lower energy than the defect caused by the different orientation of the fragment. In the frequency region where the contribution of external vibrations of the molecules is significant, the vibrations mainly involve several molecules in the cell. In the region of internal vibrations there are modes, which are local vibrations of the defects. These local vibrations involve mainly motion of the atoms constituting the defect molecule. The number of local vibrations is larger for the defect that corresponds to the formation of the structure with the OH...O hydrogen bond than for the defect that corresponds to the different orientation of the whole molecule with the OH...N hydrogen bond. The internal vibrations of the defect molecule formed by the different orientation of phenol fragment in the lattice undergoes frequency shift in relation to the frequency of the modes of isolated molecule.

A new four-dimensional ab initio potential energy surface and rovibrational spectra for the C2H2–Ar complex

ABSTRACT We report a new four-dimensional potential energy surface for the C2H2–Ar complex involving the and normal modes for the symmetric stretching and asymmetric stretching vibration of the C2H2 molecule. The potential was constructed at the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)]-F12 level with augmented correlation-consistent polarized-valence triple-zeta (aug-cc-pVTZ) basis set supplemented with midpoint bond functions (3s3p2d1f1g). Two vibrationally averaged potentials with C2H2 at the vibrational ground and excited states were obtained by the integration of the potential over the and coordinates. It was found that each averaged potential has two equivalent T-shaped global minima, two equivalent local minima as well as three saddle points among them. The global minima are located at = 3.97 Å, = 61.4°/118.6° with a well depth of 125.47 cm−1. The rovibrational energy levels and bound states were calculated adopting radial discrete variable representation (DVR)/angular finite basis representation (FBR) and the Lanczos algorithm. The calculated band origin for C2H2–Ar is red-shift by −0.9937cm−1 in the region of C2H2, which reproduces the observed value of −1.0749cm−1 successfully. Furthermore, the calculated microwave and infrared transition frequencies are in well good agreement with the experiment data.

Utilization of coconut shells in the manufacture of appropriate goods

Coconut shell inside is hard or very hard polymer, because of the composition of lignin > cellulose, such material s not good as a TV antenna. Because if given electromagnetic waves there will be vibrations of molecules >> ure rotation. To overcome this, the lignin concentration is reduced so that the concentration of lignin <cellulose can be used as a TV antenna, HP, because such material has become soft material. This combination of soft> hard polymers can theoretically be used for the purpose of detecting earthquakes, satellite etc. If the coconut is shaken, there will be ripples of coconut water to the ears, facts thus showing that the coconut shell has gaps or pores which carries waves of coconut water to the ears, which come out through the interface of lignin cellulose. The initial symptoms thus mean that the coconut shell can reflect and absorb waves. The advantages of this antenna can close up more clear, clear, cool clearer eyes and reception, can be used in the lowlands, highlands and at the bottom sea, this antenna is very good performance for high frequencies, can close up clearer, clear, cool in the eyes and voice reception clearer.

Microwave heating assistant preparation of high permselectivity polypiperazine-amide nanofiltration membrane during the interfacial polymerization process with low monomer concentration

By causing the water molecule vibration to generate heat, microwave has become a rapid and efficient heating method which is widely used in industrial production. Herein, microwave heating assistant interfacial polymerization (IP) process was innovatively applied to fabricate polypiperazine-amide nanofiltration (NF) membrane for the first time. With microwave heating, a uniform and faultless polyamide (PA) layer could be generated with low monomer concentration. The pure water flux (PWF) of the NF membrane fabricated with microwave heating was 157.1 L m-2 h-1 with the Na2SO4 rejection of 97.7% under 0.6 MPa. Meanwhile, such NF membrane showed extraordinary selectivity to Cl- and SO42− for a series of mixing solution with different concentrations. This new insight into microwave heating assistant IP provides a feasible method for the high-permselectivity NF membranes fabrication.

Plasmon enhanced low frequency stimulated Raman scattering in water due to optical breakdown in gas nanobubbles

In the current study, we evaluated the effect of presence of gas nanobubbles in water samples on nonstationary stimulated Raman scattering (SRS) of laser pulses and laser-induced optical breakdown. The SRS excitation threshold was higher and the optical breakdown threshold was lower in nanobubble-containing water compared to nanobubble-free water. The spectrum of the SRS signal from nanobubble-free water samples was found to differ from that of nanobubble-containing water samples. The SRS spectrum of water without nanobubbles contained only a narrow peak with a maximum near 3410 cm−1, which can be associated with stretching vibrations of water molecules. However, in water with nanobubbles an additional SRS signal in the frequency range of 500–1000 cm−1 with a maximum at 700 cm−1 appeared at certain pump intensities. The intensity of this signal significantly exceeded that with the maximum at 3410 cm−1. To interpret these results, we put forward a hypothesis that the detected effect is related to the huge enhancement caused by the generation of a resonance surface plasmon inside a gas nanobubble during optical breakdown. Under these circumstances, the frequency of plasmon resonance coincides with the Stokes shift frequency, and the plasmon is excited due to the beating of the pump wave and the Stokes wave. An expression for the plasmon resonance frequency as a function of the nanobubble radius was obtained.

Ring-puckering potential energy functions for cyclobutane and related molecules based on refined kinetic energy expansions and theoretical calculations

With the aid of ab initio calculations, the one-dimensional representations of the ring-puckering vibrations of several four-membered ring molecules have been refined. These one-dimensional models include contributions from MH2 (M = C, Si, Ge) rocking motions and utilize the computed parameter ω which reflects the relative amounts of ring angle bendings. This model leads to much more accurate determinations of the coordinate dependent kinetic energy expressions g44(x) which in turn allow much more accurate calculations of the ring-puckering potential energy functions (PEFs) based on experimental data. The resulting experimental PEFs agree remarkably well with the theoretical functions determined from ab initio calculations. For each molecule spectroscopic data were fit very well utilizing the refined kinetic energy functions and two term PEFs. They were fit even better using three term PEFs including x6 terms. The PEFs, barrier heights, and energy minima are presented for each of these molecules and their isotopic species.

The Structure and Vibrational Spectra of Gallium(III) Fluoride Dimeric Complex with Tetramethylammonium Cation

We have determined the crystal structure of gallium(III) fluoride dimeric complex [N(CH3)4]2[Ga2F8(H2O)2], which is composed of [N(CH3)4]+ tetrahedral cations and [Ga2F8(H2O)2]2– dimeric complex anions, formed by combining two slightly distorted GaF5(H2O) octahedral groups with a common F–F edge. By O–H···F hydrogen bonds, [Ga2F8(H2O)2]2– dimeric complex anions unite into polymer chains, between which tetramethylammonium cations are located. Based on quantum-chemical calculations, we have assigned bands in vibrational spectra of the synthesized compound. Bands that refer to vibrations of anions, cations and H2O molecules involved in hydrogen bonds have been identified in the spectra.

Static correlation in vibrational frequencies studied using thermally-assisted-occupation density functional theory

Thermally-assisted-occupation density functional theory is a method that incorporates approximate static correlation at a relatively low computational cost and allows static correlation effects to be more easily incorporated into vibrational frequency calculations. Here the effects of thermally-assisted-occupation are tested on a wide range of frequencies, indicating that static correlation plays an important role in the vibrations of several molecules that make up popular test sets of experimental vibrational frequency data. Small but persistent effects are also noted for vibrations involving significant hydrogen stretching character and mode-specific differences are seen for several molecules that are known to have multi-reference character.

Multivariate characterisation of Italian monovarietal red wines using MIR spectroscopy

Aim: The aim of this study was to investigate the application of mid-infrared (MIR) spectroscopy combined with multivariate analysis, to provide a rapid screening tool for discriminating among different Italian monovarietal red wines based on the relationship between grape variety and wine composition in particular phenolic compounds.Methods and results: The MIR spectra (from 4000 to 700 cm‒1) of 110 monovarietal Italian red wines, vintage 2016, were collected and evaluated by selected multivariate data analyses, including principal component analysis (PCA), linear discriminant analysis (DA), support vector machine (SVM), and soft intelligent modelling of class analogy (SIMCA). Samples were collected directly from companies across different regions of Italy and included 11 grape varieties: Sangiovese, Nebbiolo, Aglianico, Nerello Mascalese, Primitivo, Raboso, Cannonau, Teroldego, Sagrantino, Montepulciano and Corvina.
 PCA showed five wavelengths that mainly contributed to the PC1, including a much-closed peak at 1043 cm‒1, which correspond to the C–O stretch absorption bands that are important regions for glycerol, whereas the ethanol peaks at around 1085 cm‒1. The band at 877 cm‒1 are related to the C–C stretching vibration of organic molecules, whereas the asymmetric stretching for C–O in the aromatic –OH group of polyphenols is within spectral regions from 1050 to 1165 cm‒1. In particular, the (1175)–1100–1060 cm‒1 vibrational bands are combination bands, involving C–O stretching and O–H deformation of phenolic rings. The 1166–1168 cm‒1 peak is attributable to in-plane bending deformations of C–H and C–O groups of polyphenols, respectively, for which polymerisation may cause a slight peak shift due to the formation of H-bridges.The best result was obtained with the SVM, which achieved an overall correct classification for up to 72.2% of the training set, and 44.4% for the validation set of wines, respectively. The Sangiovese wines (n=19) were split into two sub-groups (Sang-Romagna, n=12 and Sang-Tuscany, n=7) considering the indeterminacy of its origins, which is disputed between Romagna and Tuscany. Although the classification of three grape varieties was problematic (Nerello Mascalese, Raboso and Primitivo), the remaining wines were almost correctly assigned to their actual classes.Conclusions: MIR spectroscopy coupled with chemometrics represents an interesting approach for the classification of monovarietal Italian red wines, which is important in quality control and authenticity monitoring.Significance and impact of the study: Authenticity is a main issue in winemaking in terms of quality evaluation and adulteration, in particular for origin certified/protected wines, for which the added marketing value is related to the link of grape variety with the area of origin. This study is part of the D-wine project “The diversity of tannins in Italian red wines”.

Motion of Elastic Particles and Spectrum of Hydrogen Atoms

This article analyzes the spectral structure of hydrogen atoms according to the motion theory of elastic particles. The results demonstrate that optical radiation originates from the elastic vibration of atoms or molecules. The quantum state is the equilibrium feature of the classically statistical system, and the quantum transition is the process of conversion between different motion modes.

Studying the Influence of Additives on Binding Cellulose Fibers by IR Spectroscopy

The paper is devoted to the investigation of the polymer additives’ influence on the strength properties of a sheet and to the analysis of the absorption bands related to the vibration of the groups that participated in the formation of the network of hydrogen bonds in the system: fiber–water–additive. The relation between the intensity of the absorption bands of the stretching vibration of the hydroxyl groups and the deformational vibrations of the water molecules and the functional groups with the sheet’s strength properties is presented.

Molecular Analysis of Retrogradation of Corn Starches.

Changes of the molecular dynamics of water in 5% corn starch pastes and 5% systems composed of starch and non-starchy hydrocolloid were studied during short and long term retrogradation. Low Field NMR was used to record mean correlation times (τc) of water molecules. This molecular parameter reflects the rotation of water molecules within the network of paste. Starches of different amylose and amylopectin content were selected for this study. Comparison of the changes of τc shows how particular polymers bind water molecules. During 90 days of storage, over 50% increase in mean correlation time was recorded in pastes of starches with high amylose content. This suggests that the formation of polymeric network is controlled by amylose to which water is binding. Amylopectin was found to influence the mobility of water in the pastes to a lesser extent with changes in mean correlation times of approximately 10–15% over 90 days. On retrogradation, amylopectin, Arabic and xanthan gums hindered the formation of solid phase structures. Guar gum evoked an increase in mean correlation times of approximately 40–50% during the prolonged process of changes of the molecular dynamics of water. This indicates continued expansion of the polymeric network. Mean correlation time available from spin–lattice and spin–spin relaxation times can be useful in the analysis of the rotational vibrations of the water molecules in biopolymeric structures.

Structural, magnetic and second harmonic generation properties in Mayan blue indigo nanostructured pigment

In this work, we report new results on magnetic and second harmonic generation properties found in Mayan Blue Indigo (MBI) synthetic nanostructured pigment. MBI pigment was synthesized by a conventional method. Magnetization values were found to be 6.968 × 10−2 emu/g and 18.91 × 10−2 emu/g at 300 K and 50 K, respectively. Electron paramagnetic resonance spectra indicates unpaired electron signal appearing at the g-value of 2.49 with a peak-to-peak line width of 2114 G. Second harmonic generation properties were found at 483 nm. MBI pigment was analyzed using various characterizations techniques. The nano-structure and chemical surface characterization were confirmed by techniques that included high resolution transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The characterization results indicated, acicular nanostructures of ~1.14 nm, iron nanoparticles of ~1 nm, indigo molecule vibration mode at 632.52 cm−1, and binding energies corresponding to Fe (2s, 3s), O (1s, 2s), N (1s), C (1s), Si (2s, 2p), Al (2s, 2p), Mg (2s, 2p) related to the electronic structure of MBI nanostructured pigment.