Broadband Reflection Spectra of Saccharides in the THz and IR Ranges

Optics and Spectroscopy - The reflection spectra of pure single-phase pressed samples of saccharides are measured by the methods of coherent submillimeter, pulsed terahertz, and broadband...     

Relationship between the Molecular Dynamics of Polystyrene and Its Modifications and the THz Absorption Parameters in IR Spectra

Optics and Spectroscopy - IR spectra of polystyrene (PS) and its modifications, obtained by substitution of hydrogen atoms in the benzene ring by methyl groups and/or chlorine and bromine atoms,...     

Reflection and Absorption Spectra of Fluorite in the UV Spectral Region

We have calculated the R(E) and ₁(E) spectra from the theoretical ₂(E) spectra of five models in the region 8–27 eV and the ₂(E) and ₁(E) spectra from the experimental R(E) spectrum in the region 6–35 eV. The results are compared with the known theoretical ₂(E) spectra of five models. The basic features of all of the R(E), ₂(E), and ₁(E) spectra have been revealed. It is established that the experimental R(E) spectrum and the ₂(E) and ₁(E) spectra calculated with the use of experimental data are in good agreement with the results of theoretical calculations for the models of ₂(E). On the basis of the known theoretical calculations of the fluorite zones, a scheme of the nature of the principal maxima of R(E) and ₂(E) is suggested.     

几种糖衍生物分子的THz光谱研究

分子间氢键等振动可以出现在THz波段。糖类是重要的生物分子,是研究氢键的典型体系。糖的衍生物分子具有重要的功能,同时由于它们的特殊的分子结构,通常有大量氢键存在,使得它们在THz波段表现出一定的光谱特征。文章测定了几种糖衍生物分子的THz光谱,结果表明不同分子具有不同的光谱,异丙基-β-D-硫代葡萄糖具有1.17,1.35,1.93,2.23 THz等多个吸收峰;异丙基-β-D-硫代半乳糖的吸收峰位于1.93 THz处;甲基-(四-氧-乙酰基-β-D-半乳糖)的吸收峰位于1.87 THz处;氧-(2, 3, 4, 6-四-氧-乙酰基-β-D-葡萄糖)-氮-羟基琥珀酰亚胺具有1.23,1.70,1.84,2.23 THz等多个吸收峰。对结构相似的分子,尤其对于异构体来说,它们具有不同的峰位,这些低频振动为包含氢键在内的整个分子的振动,说明THz方法能够鉴别异构体,是对结构变化、空间构型等很敏感的技术,是红外光谱的有益补充。这也为大分子的光谱研究提供了基础。     

Profile Shape of Absorption Spectra in the IR Spectra of Carbohydrates

In the IR spectra of mono-, di-, and polysaccharides, the profile shapes of eight absorption bands have been investigated. They turned out to be symmetric and very close to the dispersion one for all the bands considered. It has been found that in mono- and disaccharides the minimum halfwidth of the bands is 10 cm^–1 and in polysaccharides it is higher by a factor of two or more. The halfwidth ratios of different bands in one and the same spectrum can differ severalfold. As is shown, double differentiation of the IR spectra makes it possible to investigate the profile shape of absorption bands when there is marked background absorption or these bands significantly overlap with other bands.     

Absorption Spectra of Excited Ruby Crystals

We have investigated the absorption spectra of excited laser single crystals of ruby. The longlived increase in absorption depending on the degree of excitation is observed in optically excited crystals of ruby in a wide spectral range. Moreover, in the absorption spectrum of a postexcited ruby we discovered the excitationinduced longlived kinetic instability, namely, the noiselike quasiline component variable in time and over the spectrum and imposed on the smooth spectral curve.     

Intermolecular Interactions in 8-Aza-D-Homogonane Crystals and their Manifestation in the IR Spectra

Crystalline modifications of 8-aza-D-homogon-1,3,5(10),13-tetraen-12,17a-dione have been investigated by IR spectroscopy and x-ray structural analysis. It is shown that this compound crystallizes from solutions of chloroform with hexane in the form of a solvate comprised of chelate hydrogen bonds between the hydrogen atom of the chloroform molecule and the oxygen atoms of the carbonyl groups of the 8-azasteroid molecule. A relation between the changes in the characteristic absorption bands of the CH₂-, C=O-, and I=C groups and the structure of the crystalline modifications has been established.     

Absorption Spectra of Single Crystals of EuGa2S4 and EuGa2S4:Co

The optical properties of EuGa₂S₄ and EuGa₂S₄:Co single crystals in a range of temperatures from 77 to 300 K are investigated. The single crystals are obtained by the Bridgman method and are characterized by tetragonal syngony. The behavior of the optical transitions in the photon energy range 1.70–2.45 eV and the temperature range 77–300 K is determined. It is established that in the energy range 1.77–1.90 eV absorption is associated with transitions of the Co²⁺ ion, while in the range 2.20–2.40 eV, with indirect allowed optical transitions.     

晶体NiF2的吸收光谱和电子顺磁共振谱的一种完全对角化计算

采用半自洽场(semi-SCF)自由Ni²⁺的d轨道波函数、点电荷-偶极子模型和Ni²⁺-6X^-(X=F,Cl,Br,I)络合物的μ-κ-α模型,建立结构参数与光谱、电子顺磁共振(EPR)谱(零场分裂D,E和顺磁g因子)之间的定量关系.利用能量矩阵完全对角化方法(CDP)和高阶微扰方法,统一解释NiF₂晶体的局部结构、吸收光谱和电子顺磁共振谱(EPR).比较两种方法计算得到的零场分裂D,E和顺磁g因子.结果表明:①高阶微扰方法算出的D,E值误差大;②能量矩阵完全对角化方法(CDP)算出的D,E值、光谱、顺磁g因子的值都与实验符合很好.     

Properties of IR Absorption Spectra of Bi-Pb-Sr-Ca-Cu-O Superconducting Material

Abstract

We used the co-decomposition method to make the Bi(Pb)-Sr-Ca-Cu-O superconductor samples (T_c = 112K) under oxygen partial pressure. Oxygen dependence of high-T_c phase was studied. The infrared absorption spectra of (Bi_1?xPb_x)₂Sr₂Ca₂Cu₃O_10+σ superconductor were measured at various temperatures from 98 to 290K. A new IR absorption peak was observed at 1265 cm^?1 below 217K. The intensity of this peak became stronger with temperature decreasing.     

Determination of Stoichiometry,Concentration of OH Groups,and Point Defects in Lithium Niobate Crystals from Their IR Absorption Spectra

Optics and Spectroscopy - The concentration of OH impurity groups, the Li/Nb ratio, the concentration of Nb $$_{{{\text{Li}}}}^{{4 + }}$$ and V $$_{{{\text{Li}}}}^{ - }$$ point defects in...     

Nonlinear Optical Characteristics of BSO and BGO Photorefractive Crystals in Visible and Infrared Ranges

Nonlinear refraction, nonlinear absorption and optical limiting in photorefractive crystals Bi₁₂SiO₂₀(BSO) and Bi₁₂GeO₂₀(BGO) at the wavelengths of 1064 and 532 nm were investigated. It was shown that both BSO and BGO crystals possess by positive nonlinear refraction in two investigated spectral ranges (n ₂ ^BSO=(2.5 ± 0.5)× 10^–12 esu, n ₂ ^BGO=(6.3 ± 1.3)× 10^–12 esu at equals 1064 nm; n ₂ ^BSO=(4.4 plusmn; 0.9)× 10^–12 esu, n ₂ ^BGO=(7.4 ± 1.5)× 10^–12 esu at = 532 nm). The nonlinear absorption was due to three-photon absorption at the wavelength of 1064 nm ( ⁽³⁾ _BSO=(2.5 ± 0.8)× 10^–20cm³W^–2, ⁽³⁾ _BSO=(4.4 ± 1.3)× 10^–20cm³W^–2) and two-photon absorption at the wavelength of 532 nm ( ⁽²⁾ _BSO=(2 ± 0.4)× 10^–9cm W^–1, ⁽²⁾ _BGO=(3.7 ± 0.7)× 10^–9cm W^–1).     

EPR and Optical Absorption Study of Cu2+-Doped Diammonium Hexaaqua Magnesium Sulphate Single Crystals

Electron paramagnetic resonance (EPR) study of Cu²⁺ ions doped in diammonium hexaaqua magnesium sulphate single crystal over the temperature range of 4.2–320 K is reported. Copper enters the lattice substitutionally and is trapped at two magnetically equivalent sites. The spin Hamiltonian parameters are evaluated at 320, 300, 77, and 4.2 K. The angular variations of the resonance lines in three mutually perpendicular planes ab, bc* and c*a are used to determine principal g and A values. The observed spectra are fitted to a spin Hamiltonian of rhombic symmetry with parameters of Cu²⁺ at 77 and 4.2 K: g _xx  = 2.089, g _yy  = 2.112, g _zz  = 2.437 (±0.002) and A _xx  = 38, A _yy  = 14, A _zz  = 110 (±2) × 10^?4 cm^?1. The ground state wave function of Cu²⁺ ion in this lattice is determined. The g-factor anisotropy is calculated and compared with the experimental value. The optical absorption spectra of the crystal are also recorded at room temperature. With the help of assigned bands the crystal-field parameters (Dq, Ds and Dt) are evaluated. By correlating the optical and EPR data, the nature of bonding in the complex is discussed. The temperature dependence of the g values is explained to conclude the occurrence of both static and dynamic Jahn–Teller effects over the temperature range of investigation.     

Optical Spectra of GaSe and GaS Crystals of Different Thicknesses

Physics of the Solid State - The transmission spectra of GaSe and GaS crystals of different thicknesses prepared by mechanical stratification of bulk crystals have been investigated. The...     

Optical Absorption Spectra and Intraband Dynamics in Terahertz-Driven Semiconductor Superlattice

We have theoretically investigated the optical absorption spectrum and intraband dynamics by subjecting a superlattice to both a terahertz (THz)-frequency driving field and an optical pulse by using an excitonic basis.In the presence of a THz dc field, the satellite structures in the absorption spectra are presented. The satellite structure is a result from the THz nonlinear dynamics of Wannier-Stark ladder excitons. On the other hand, the coherent intraband polarization is investigated. We find that the excitonic Bloch oscillation is driven by the THz field and yields an intraband polarization that continues to oscillate at times much longer than the intraband dephasing time. The temporal evolution of the slowly varying components of the intraband polarization is dependent on the THz frequency.     

吐昔烯衍生物分子的电子光谱与非线性光学性质

采用含时密度泛函理论(TDDFT)B3LYP对5个吐昔烯及其衍生物分子的吸收光谱进行理论计算。结果表明,该5个分子的吸收波长在281—307 nm范围内,属于近紫外区。使用有限场(FF)方法理论计算5个化合物分子的非线性光学(NLO)性质。结果显示,吐昔烯分子引入烷氧基将明显增大二阶和三阶非线性光学性质（b0和 值）,此类化合物分子的三阶非线性光学性质明显优于二阶非线性光学性质。     

EPR, Optical Absorption and Superposition Model Study of Fe3+-Doped Ammonium Dihydrogen Phosphate Single Crystals

X-band electron paramagnetic resonance (EPR) studies are carried out on Fe³⁺ ions doped in ammonium dihydrogen phosphate (ADP) single crystals at room temperature. The crystal field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations. The obtained values of spin Hamiltonian and zero-field parameters of the Fe³⁺ ion in ADP are: g = 1.994 ± 0.002, |D| = (220 ± 5) × 10^?4 cm^?1 and a = (640 ± 5) × 10^?4 cm^?1. On the basis of EPR data, the site symmetry of the Fe³⁺ ion in the crystal is discussed. The Fe³⁺ ion enters the lattice substitutionally replacing the NH₄ ⁺ sites. The optical absorption of the crystal is also studied at room temperature in the wavelength range of 195–925 nm. The energy values of different orbital levels are calculated. The observed bands are assigned as transitions from the ⁶ A _1g (S) ground state to various excited quartet levels of the Fe³⁺ ion in a cubic crystalline field. From the observed band positions, Racah interelectronic repulsion parameters (B and C), cubic crystal field splitting parameter (D _q ) and Trees correction are calculated. There values are: B = 970, C = 1,923, D _q  = 1,380 cm^?1 and α = 90 cm^?1, respectively. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The zero-field splitting (ZFS) parameters are also determined theoretically using B _kq parameters estimated from the superposition model. The values of ZFS parameters thus obtained are |D| = (213 ± 5) × 10^?4 cm^?1 and |E| = (21 ± 5) × 10^?4 cm^?1.     

Optical Spectra of Gamma-Irradiated LiF Crystals with Anisotropic Lithium Nanoparticles

The optical response of Li anisotropic defects and nanoparticles from three faces of cubic LiF crystals with 10-mm edges to γ radiation from a ⁶⁰Со source with doses of 10⁵–10⁹ R at 320 K in air is studied. After a maximum dose of 10⁹ R, scanning electron microscopy revealed submicron metal lithium flakes ordered into long parallel nanofilaments. The resonance absorption band, which shifts from 272 to 295 nm with increasing dose, is assigned to lithium nanocolloids in the (110) plane. The band at 202–225 nm observed only from the (100) face narrows at doses below 10⁵ R and is assigned to diatomic fluorine molecules in interstitial sites. The appearance of the 209–212–215-nm triplets at 2.7 × 10⁵ R from the (100) plane and the 211–213–215-nm triplets at 0.9 × 10⁵ R from the (010) plane is related to radiation-induced axially symmetric bipolarons with a high oscillator strength. The splitting of the 445-nm band into a 438–445–450-nm triplet is observed only for the (010) plane after a dose of 10⁶ R and is related to surface plasmon polaritons (longitudinal and transverse) of elongated Li nanoparticles. The (F₂–F₃) complexes are oriented in the most imperfect (111) plane and are seen along three cubic axes.