Calculation of the intensity and dichroism of the IR absorption bands of oriented polymers

An algorithm for calculating the intensity and dichroism of polarized IR absorption bands of oriented polymers is proposed. The absorption curves in the IR spectrum of amorphous cis-1,4-polyisoprene and the dichroism of its absorption bands have been calculated. The polarization IR spectra of oriented amorphous cis-1,4-polyisoprene for a stretching ratio equal to 3 have been constructed. The calculated values of the absorption-band dichroism are in fairly good agreement with the experimental data.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 129–132, January–February, 2005.     

Theoretical Study into the Dichroism of the Absorption Bands in the IR Spectra of Oriented Polymers

The IR dichroism of the polarized absorption bands of oriented polymers has been considered. An equation has been obtained that makes it possible to calculate the dichroism of the absorption bands for a different degree of the polymer orientation. This equation has been simplified especially for structurally insensitive absorption bands. In this case it allows one to determine the type of polarization of absorption bands.     

Polarized Raman and photoluminescence studies of a sub‐micron sized hexagonal AlGaN crystallite for structural and optical properties

The polarized Raman spectroscopy is capable of giving confirmation regarding the crystalline phase as well as the crystallographic orientation of the sample. In this context, apart from crystallographic X‐ray and electron diffraction tools, polarized Raman spectroscopy and corresponding spectral imaging can be a promising crystallographic tool for determining both crystalline phase and orientation. Sub‐micron sized hexagonal AlGaN crystallites are grown by a simple atmospheric pressure chemical vapor deposition technique using the self catalytic vapor–solid process under N‐rich condition. The crystallites are used for the polarized Raman spectra in different crystalline orientations along with spectral imaging studies. The results obtained from the polarized Raman spectral studies show single crystalline nature of sub‐micron sized hexagonal AlGaN crystallites. Optical properties of the crystallites for different crystalline orientations are also studied using polarized photoluminescence measurements. The influence of internal crystal field to the photoluminescence spectra is proposed to explain the distinctive observation of splitting of emission intensity reported, for the first time, in case of c‐plane oriented single crystalline AlGaN crystallite as compared with that of m‐plane oriented crystallite. Copyright © 2016 John Wiley & Sons, Ltd.     

Role of Light Polarization in the Optothermal Effect

It is shown that the highest optothermal effect in low-intensity irradiation is attained on chromophores of stationary orientation exposed to irradiation by a linearly polarized light. For chromophores with stochastization of orientation between the events of light absorption, the magnitude of the optothermal effect is independent of polarization and is three times lower than in stationary orientation. In anisotropic media, an optimally oriented linearly polarized light is more efficient.     

Simulation of the influence of the polymer conformation,orientation, crystallinity,and stretching on its IR absorption spectrum

Using cis-1,4-polyisoprene as an example, the influence of the conformation and orientation of the polymer chain on its polarization absorption spectra has been simulated. It has been shown that if a change in the orientation of the polymer chain leads to a monotonic change in the intensities of the absorption bands with their maxima positions remaining unchanged, then changes in the polymer chain conformation additionally cause a shift and the appearance of new absorption bands. According to the results of the calculation of the vibrational spectra, the inversion of the IR dichroism of the absorption bands of polymers is associated with the conformation transition. We simulate the influence on the IR absorption spectrum of the degree of crystallinity of cis-1,4-polyisoprene, in which the amorphous and amorphous-crystalline states are considered as a mixture of noninteracting polymer chains, where each state is characterized by a certain ratio of conformers. Likewise, the changes in the IR absorption spectrum of cis-1,4-polyisoprene under its stretching have been investigated. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 727–733, November–December, 2005.     

Experimental and theoretical investigation of vibrational spectra of copper phthalocyanine: polarized single‐crystal Raman spectra,isotope effect and DFT calculations

The IR‐ and Raman spectra of copper phthalocyanine (CuPc), as well as the isotopic wavenumber shifts upon ¹⁵N substitution in CuPc, were investigated experimentally and theoretically. The symmetry of molecular vibrations was determined using polarized Raman spectra of an oriented CuPc single crystal. Density functional theory (DFT) calculations were used for the detailed assignment of different bands in the vibrational spectra of CuPc. Theoretically predicted geometry, wavenumbers and isotopic shifts are in a very good agreement with the experimental values. A comparison of experimentally obtained isotopic shifts with theoretical predictions allowed us to reveal some characteristic features of normal vibrations of CuPc molecule. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman tensor analysis of hexagonal polyoxymethylene and its application to study the molecular arrangement in highly crystalline electrospun nanofibers

The orientation dependence in space of Raman‐active vibrations in the hexagonal structure of polyoxymethylene (POM) is discussed in terms of Raman tensor elements as intrinsic physical parameters of the lattice. The variation of polarized intensity for the A₁ and the E₁ vibrational modes with respect to the POM molecular orientation is systematically studied, from both theoretical and experimental viewpoints, according to the symmetry assignments of each vibrational mode. A set of working equations including the Raman selection rules associated with the A₁ and the E₁ modes and the orientation distribution function are explicitly formulated and validated by means of a least‐square fitting procedure on experimental data. In addition, an approach based on the introduction of orientation distribution functions is applied to quantitatively assess and compare on a statistical base the molecular orientation of two different types of electrospun POM nanofibers. Copyright © 2012 John Wiley & Sons, Ltd.     

单轴取向分子在垂悬液滴界面上的Raman图像理论分析

提出并建立了表面单分子膜在垂悬液滴面上的Ｒａｍａｎ图像取向的确定方法。对具有单以向性的分子，推导出全部Ｒａｎａｍ散射活性矩阵元，计算并给制了Ｒａｍａｎ图像的光强分布以及确定分子取向的偏振光强比分布。     

快速测量扭曲向列相液晶盒盒厚

提出了一种利用圆偏光仪测量扭曲向列相液晶盒盒厚的新方法,即:圆偏光仪组成为两端是一对起偏器和检偏器,中间放置一对四分之一波片.起偏器和检偏器平行或垂直放置,其中一个四分之一波片的快轴和起偏器透光轴成45°,另一个四分之一波片的快轴和起偏器透光轴成－45°.液晶盒样品直接插入到两四分之一波片中间,无需调整方向.不同于旋转液晶盒或偏振片寻找输出光强最大值或最小值的方法,圆偏光仪测量盒厚不需要旋转任何光学元件或液晶盒观测输出光强的变化,只需要观测检偏器在平行和垂直方向的两个强度值,能够实现快速测量,简洁而且有效.     

用偏振荧光光谱表征乙醇-水团簇分子的取向行为

采用波长为236nm紫外光激励乙醇水溶液获得荧光光谱并对其偏振特性进行了研究.实验中分别改变入射光的偏振度，在300—400nm波段内进行荧光光谱、水平和垂直偏振荧光光谱检测.实验结果表明，当采用线偏振光照射乙醇水溶液时，其发射的荧光具有一定的偏振性，并计算了其偏振度.经理论分析得到了描述荧光偏振态的四个斯托克斯矢量，进而对该荧光的偏振状态进行了描述，通过对乙醇-水溶液的米勒矩阵的计算，对溶液中分子的取向特性进行了分析.本结果能对乙醇-水团簇分子的结构提供理论参考. 关键词： 荧光光谱 偏振光谱 斯托克斯矢量 米勒矩阵     

Study on dipolar orientation and relaxation characteristics of guest-host polymers affected by corona poling parameters

The dipolar orientation and relaxation characteristics of guest-host polymers poled by corona poling have been studied in detail. The mechanisms of dipolar orientation affected by poling parameters (voltage, temperature, time and cooling velocity) in polymers have been analyzed by UV-Vis absorption spectra and microscope. The results show that with increasing poling voltage, the orientation order parameter increases to maximum and then drops. Also the same trend of orientation order parameter has been obtained with increasing poling temperature. While the orientation order parameter increases to saturation with increasing poling time. With the biexponential model analyzing, it is shown that the relaxation of dipolar orientation can be slowed by slowing the cooling velocity during the poling process.     

Polarized Infrared and Raman Spectra and Ab-Initio Calculations of 2-(Methylthio)Benzothiazole

Abstract

The infrared spectra of 2-(methylthio)benzothiazole have been measured from 4000 to 180 cm^?1 for liquid and polycrystalline samples, polarized spectra of oriented films have also been obtained. the Raman spectra of polycrystalline and liquid samples have been investigated. the structural parameters, energies and vibrational frequencies have been calculated from ab-initio RHF calculations using the 6-31G?? basis set for various conformations. a detailed assignment of most of the observed bands has been proposed on the basis of the infrared dichroism, Raman polarization data and frequency calculations.     

Polarization and intensity of Compton scattering

X-ray spectra scattered at 90° by acrylic resin plates of various thicknesses are measured. The intensity and polarization of Compton-scattered X-rays are estimated from the spectra. As the thickness of the slab increases, the intensity increases but the polarization decreases. The optimal thickness for a polarized X-ray fluorescence spectrometer is determined, which provides both high intensity and high polarization.     

Control of Spontaneous Emission via a Single Elliptically Polarized Light in a Five-Level Atomic System

We investigate the features of the spontaneous emission spectra in a cold five-level atomic system coupled by a single elliptically polarized control field. We use wave function approach to derive the explicit and analytical expressions of atomic spontaneous emission spectra. It is shown that some interesting phenomena such as spectralline enhancement, spectral-line suppression, spectral-line narrowing, spectral-line splitting and dark fluorescence can be observed in the spectra by appropriately modulating the phase difference between the right-hand circularly (LHC) and left-hand circularly (RHC) polarized components of the elliptically polarized control field and the intensity of external magnetic field. The number of emission peaks, the positions of fluorescence-quenching points can be also controlled. Furthermore, we propose an ultracold 87Rb atomic system for experimental observation. These investigations may find applications in high-precision spectroscopy.     

Effect of polymer adsorption on the water structure at the quartz/water interface studied by optical sum frequency generation

The effect of polymers weakly adsorbed on a quartz surface on the structure of the interfacial water molecules was investigated by optical sum frequency (SF) spectroscopy. As polymers, poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and two types of tri-block copolymer of Pluronic L64 and 17R-4 were used. SF intensity spectra of OH stretching mode of water molecules at the interface between a quartz substrate and aqueous solutions of the polymers were measured. The total SF intensity of the interfacial water of the L64 aqueous solution was smaller than those of other solutions. This result indicates that the L64 aqueous solution has smaller number of oriented interfacial water molecules. It is suggested that the rapid motion of hydrophilic parts of the adsorbed L64 disturbs the average orientation of the interfacial water molecules. On the other hand, the SF intensity from the interfacial water molecules of aqueous solutions with high ion strength did not depend on the species of the polymers in the solutions. The latter result suggests that the hydration of ions determines the structure of the interfacial water molecules.     

Raman polarization studies of highly oriented organic thin films

In this work we report on the capability of polarized Raman spectroscopy to investigate the structure of thin organic films. Diindenoperylene (DIP) thin films on (1 × 1)‐rutile(110) were prepared via organic molecular beam deposition (OMBD). Raman spectra of DIP thin films showed several strong Raman modes in the wavenumber region from 1200 to 1650 cm⁻¹. The A_g mode at 1284 cm⁻¹ shows two contributions, thereby indicating the coexistence of at least two DIP film structures. Polarized Raman spectroscopy was applied to characterize the molecular orientation and the dominance of the σ‐configuration (i.e. upright standing DIP molecules) was found. Copyright © 2009 John Wiley & Sons, Ltd.     

Calculation of polarized IR absorption spectra for trans-1,4-polyisoprenes of various conformations

Polarized IR spectra for two conformations of trans-1,4-polyisoprene (α-and β-gutta-percha) were calculated. The IR dichroism of the absorption bands was calculated for both conformations. The computed results for polarized IR spectra and IR dichroism agree reasonably well with the respective experiment data. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 470–475, July–August, 2008.     

Improved phase demodulation for grain orientation measurement

The method of phase demodulation for wood grain orientation measurement has been improved by employing a laser sampling system instead of a laser scanning system and using an edge detection algorithm rather than an intensity detection algorithm. The laser sampling system is able to determine the average grain angle and estimate the wood defect distribution much faster and more accurate than the laser scanning system. The edge detection algorithm is able to transform not only an oriented laser pattern but also an oriented wood texture into a periodic histogram. For the hardwoods with weak tracheid effect but the texture direction indicative of the grain orientation, the orientation measurement of laser pattern can be replaced by the orientation measurement of wood texture.     

Temperature influence on the intensity of water bands ν(OH) in IR spectra of some silicate minerals

An investigation is made of the temperature dependences of the intensities of bands ν(OH) in the IR spectra of talc, quartz, and muscovite under cooling-heating conditions in ranges of 93–300 and 300–673 K. In the 93–300 K range two types of water with reversible and irreversible temperature dependences of the absorption-band intensities in the IR spectra of these minerals are revealed. The types of bound water are separated in space, apply to the volume and surface of the minerals, and their absorption bands have temperature coefficients of intensity which differ in value and sign. Institute of Geology of the Karelian Scientific Center of the Russian National Academy of Sciences, 11, Pushkinskaya St., Petrozavodsk, 185610, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 124–127, January–February, 1999.     

Different angle-resolved polarization configurations of Raman spectroscopy: A case on the basal and edge plane of two-dimensional materials

Angle-resolved polarized Raman(ARPR) spectroscopy can be utilized to assign the Raman modes based on crystal symmetry and Raman selection rules and also to characterize the crystallographic orientation of anisotropic materials.However, polarized Raman measurements can be implemented by several different configurations and thus lead to different results. In this work, we systematically analyze three typical polarization configurations: 1) to change the polarization of the incident laser, 2) to rotate the sample, and 3) to set a half-wave plate in the common optical path of incident laser and scattered Raman signal to simultaneously vary their polarization directions. We provide a general approach of polarization analysis on the Raman intensity under the three polarization configurations and demonstrate that the latter two cases are equivalent to each other. Because the basal plane of highly ordered pyrolytic graphite(HOPG) exhibits isotropic feature and its edge plane is highly anisotropic, HOPG can be treated as a modelling system to study ARPR spectroscopy of twodimensional materials on their basal and edge planes. Therefore, we verify the ARPR behaviors of HOPG on its basal and edge planes at three different polarization configurations. The orientation direction of HOPG edge plane can be accurately determined by the angle-resolved polarization-dependent G mode intensity without rotating sample, which shows potential application for orientation determination of other anisotropic and vertically standing two-dimensional materials and other materials.