Polarization modes in the Ba<Subscript>2</Subscript>Mg<Subscript>2</Subscript>Fe1<Subscript>2</Subscript>O<Subscript>22</Subscript> multiferroic

The spectra of complex permittivity of a Ba₂Mg₂Fe₁₂O₂₂ single crystal belonging to the family of Y-type hexaferrites have been measured over a wide temperature range (10–300 K) with the aim of determining the dynamic parameters of the phonon and magnetic subsystems in the terahertz and infrared frequency ranges (3–4500 cm⁻¹). A factor-group analysis of the vibrational modes has been performed, and the results obtained have been compared with the experimentally observed resonances. The oscillator parameters of all nineteen phonon modes of E _u symmetry, which are allowed by the symmetry of the Ba₂Mg₂Fe₁₂O₂₂ crystal lattice, have been calculated. It has been found that, at temperatures below 195 and 50 K, the spectral response exhibits new absorption lines due to magnetic excitations.     

Analytical method for studying terahertz vibrations in a stearic acid single crystal

The anisotropy of terahertz absorption was investigated for a B-form single crystal of stearic acid. A polarized terahertz spectrometer was used to obtain absorption spectra over the range of 1–5 THz. Seven vibrational modes were observed; four exhibited significant angular dependence. Additionally, we demonstrated a simple approach for estimating the angle of the dipole moment for each vibrational mode.     

Vibrational studies of lithium-intercalated SnSySe2−y (0≤y≤2) layered compounds

We report the vibrational properties of lithium-intercalated SnS_ySe_2−y (0≤y≤2) layered compounds. Infrared absorption spectra have been recorded as a function of temperature in the frequency range 50–600 cm⁻¹. The new bands are interpreted as vibrational modes of lithium atoms against the nearest-neighbouring-chalcogen atoms located in the van der Waals gap. Results are analyzed in terms of stretching vibrations of Li-S₄ and Li-S₆ entities. From a comparison of the spectra, it is concluded that lithium ions are more likely to occupy tetrahedral sites in the lithium-rich phases. Using a simple model of lattice dynamics, the coupling force constants are determined and compared with those of the pristine materials. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995     

Multiphonon absorption in a MgO single crystal in the terahertz range

The reflection and transmission spectra of a MgO single crystal at frequencies of 10–1000 cm⁻¹ in the temperature range 10–300 K have been measured using submillimeter and infrared Fourier spectros-copy. The evolution of anharmonic absorption with variations in temperature has been investigated in the frequency range below the frequency of the transverse optical phonon. The parameters of the dispersion model that adequately describes the lattice absorption of terahertz radiation in single-crystal magnesium oxide have been determined.     

呋喃妥因的太赫兹光谱分析

利用太赫兹时域光谱技术测量了硝基呋喃类药物中呋喃妥因原药在0.2～1.8 THz范围内的吸收系数、折射率等光学指纹特性,结果表明呋喃妥因在该频率范围内出现了多个强度不同的特征吸收峰,吸收系数光谱可用于鉴定呋喃妥因。借助Gaussian软件利用密度泛函理论对呋喃妥因分子在0.2～1.8 THz范围内的吸收系数光谱进行了模拟,并对吸收系数实验光谱中部分吸收峰的振动模式进行了分析和指认。结果表明实验谱中1.25和1.60 THz处的吸收峰与理论谱中1.30和1.67 THz处吸收峰一致,是由呋喃妥因分子内的振动模式引起的。     

有机磷农药甲基对硫磷的太赫兹(THz)光谱研究

运用太赫兹时域光谱技术(THz-TDS)与理论模拟相结合的方法研究了有机磷农药甲基对硫磷在THz波段的光谱特性。在室温氮气环境中得到了样品在0.2～2.0 THz波段的吸收谱和折射率谱。表明其特征吸收峰分别位于0.65,1.33,1.81和1.91 THz处,其平均折射率为1.39。同时运用密度泛函理论(DFT)计算了甲基对硫磷分子的结构及其在太赫兹波段的振动频率,计算结果与实验数据吻合较好。研究结果表明,实验光谱的特征吸收峰是由分子的集体振动及扭转形成,不同的吸收峰位对应分子不同的振转模式。     

THz wave sensing for petroleum industrial applications

We present the results of terahertz (THz) sensing of gasoline products. The frequency-dependent absorption coefficients, refractive indices, and complex dielectric constants of gasoline and xylene isomers were extracted in the spectral range from 0.5–3.0 THz. The THz spectra of gasoline (#87, #89, #93) and related BTEX (benzene, toluene, ethylbenzene, and xylene) compounds were studied by using Fourier transform infrared spectroscopy (FTIR) in the 1.5–20 THz (50–660 cm⁻¹). The xylene isomers, which are used as antiknock agent in gasoline were determined quantitatively in gasoline in the THz range. Our investigations show the potential of THz technology for the petroleum industrial applications.     

除虫脲和高效氯氟氰菊酯的太赫兹光谱及密度泛函理论研究(英文)

利用太赫兹时域光谱技术及密度泛函理论对两种常用的卫生杀虫剂除虫脲和高效氯氟氰菊酯的低频振动光谱进行了研究。室温下观测到两种物质在0.2～2.2THz内的实验谱分别有5和7个吸收峰,可作为其在THz波段的指纹谱用于分子识别。为了深入理解太赫兹吸收峰的振动特性,我们采用Gaussi-an03和CRYSTAL09软件分别进行了单分子和晶体的密度泛函理论模拟。晶体模拟结果预测出两种物质在0.2～2.2THz实验谱中所有的吸收峰,明显优于单分子模拟结果。最后通过晶体密度泛函理论模拟的简正模式分析获得不同吸收峰处的振动模式归属。结果证明太赫兹光谱技术在农药分子识别以及晶体密度泛函理论模拟在太赫兹吸收峰指认和振动模式归属方面的可行性。     

IR spectroscopy of the structural states of ethylene in aerogel nanopores

We have investigated for the first time the combination vibrational absorption bands ν₅ + ν₉ and ν₁ + ν₁₁ of ethylene adsorbed by nanopores of a silicon dioxide aerogel in the 5800–6300 cm^–1 region. Our measurements show significant differences in the absorption spectra of gas-phase ethylene and ethylene found in the nanoporous structure of the aerogel, including a change in the shape of the absorption band contours, their frequency shift, and an increase in the absorption intensity.     

FOX-7转晶行为的太赫兹光谱及理论计算研究

1, 1 -二氨基- 2, 2 -二硝基乙烯(FOX-7)是一款新型高能钝感炸药, 为了研究温度变化对其分子结构特性的影响, 利用太赫兹时域光谱技术对持续升温(298K→393 K)过程中FOX-7 在0.2—2.5 THz 频率范围内的吸收光谱进行了在线探测, 结果发现随着样品温度的升高, FOX-7 的吸收谱带发生变化, 于384 K 时出现一个新的吸收特征峰, 且该吸收峰的峰强逐渐升高. 基于密度泛函理论(DFT), 对样品在298 K 和393 K 温度下的晶体结构进行了小于2.5 THz 范围内吸收频谱的模拟计算, 完成了对FOX-7 两种晶型实验吸收特征峰的指认. 分析表明FOX-7 的分子结构会受温度的影响而发生改变, 互为异构晶型的基团表现出的振动模式不同, 温度384 K 时FOX-7 开始发生α→β 晶型转变, 且该晶型转变过程是可逆的, 新出现的1.12 THz 特征峰在393 K 时的振动是由—NO₂ 和—NH₂ 的摆动及各自的扭动所致.     

Low-frequency vibrational modes of glutamine

High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experimental and the computational results, the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations. Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.     

IR spectrum of the closed form of indolinospironaphthooxazine

IR absorption spectra of indolinospironaphthooxazine (ISNO) are presented. The geometric structure and normal coordinates of the ISNO molecule have been calculated using a quantum mechanical DFT method. The IR spectrum of ISNO in its original spiro form has been interpreted for the first time. Four normal modes in the range 800–1200 cm^–1 with the largest amplitudes of C_spiro–O bond change are identified. The excited ISNO molecule spiro form may experience photoconversion to the merocyanine form through them.     

Calculation of frequencies of normal vibrations and interpretation of IR spectra for 2,3-dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinone derivatives

We have used B3LYP/6-31(d) density functional theory to calculate the frequencies and modes of the normal vibrations of 2-oxo-2,3-dihydro-and 2-methoxy-1,4-naphthoquinones. Based on these calculations within an additive model, we have assigned the carbonyl bands in the IR spectra of 2,3-dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinones (diquinones 1–4). We have carried out a direct calculation of the vibrational spectra for diquinones 1–4 using PBE and B3LYP correlation functionals. We have shown that the calculation of the vibrational spectra of the diquinones based on an additive model on the whole is quite consistent with the results of direct calculations and the experimental spectra. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 713–720, November–December, 2006.     

Absorption spectra of benzene-isooctane mixtures in the wavelength range 1620–1820 nm

Experimental absorption spectra of benzene, isooctane, and their mixtures are obtained in the wavelength range λ = 1620–1820 nm in which the first overtones of vibrational frequencies of CH, CH₂, and CH₃ hydrocarbon groups are located. Positions of fundamental absorption bands of benzene are refined. Absorption spectra of benzene-isooctane mixtures are shown to intersect in a narrow area near λ ≈ 1695 nm. The main maximum of benzene absorption at λ = 1671.5 ± 0.5 nm, where the influence of isooctane absorption is practically absent, is proposed for determining the content of benzene in benzene-isooctane mixtures. A linear calibration curve for λ = 1671.5 nm that encompasses the full range of benzene concentrations (0–100%) is presented. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 631–634, September–October, 2008.     

Electronic spectra of cationic forms of meso-tetrapropylporphin in a nanoporous silicate gel matrix

We have studied the fluorescence and fluorescence excitation spectra at 300 K, 77 K, and 4.2 K for silicate gel matrices colored with meso-tetrapropylporphin by impregnation of the matrix with a solution of the pigment. Comparison of the data obtained with the absorption spectra in acidified solutions and analysis of the low-temperature fine-structure vibronic spectra, and also taking into account data obtained earlier for octaethylporphin in a xerogel showed formation of two cationic forms of meso-tetrapropylporphin in the gel matrix: the short-wavelength form has a dicationic structure, while the long-wavelength form has a monocationic structure. We have traced out the correlations of the vibrational structure in the spectra of the dicationic form with data for the porphin dication, and we have drawn a number of conclusions concerning the normal vibrational modes that are active in the vibronic fluorescence and absorption spectra of the studied cationic forms. Using the AM1 semiempirical quantum chemical method, we optimized the geometry of the mesotetrapropylporphin dication: the most stable of the possible conformers is the dication structure with saddleshaped macrocycle nonplanarity. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 453–461, July–August, 2006.     

持久性有机物硫丹的太赫兹光谱研究

以最新被斯德哥尔摩公约列入持久性有机污染物的硫丹为研究对象,采用太赫兹时域光谱技术获得了α硫丹在0.2～2THz频率范围内的吸收系数谱和折射率谱,结果显示在此频率范围内存在有一系列特征吸收峰,并且通过实验和理论计算对比发现在1.70和1.88THz处的实验吸收峰与1.68和1.91THz处的理论吸收峰有很好的吻合;经分析认为,这吻合峰是由于分子内集体振动引起的,实验中的其他峰值可能归因子分子间弱相互作用力和混合振动。研究结果证明了THz-TDS技术进行持久性有机物检测的可行性,为THz-TDS系统在持久性有机物识别和残留物检测方面的应用提供了依据。     

Optical investigation of CdS quantum dots in Langmuir–Blodgett films

Structures with CdS quantum dots produced by the Langmuir–Blodgett (LB) technique were investigated by Raman, IR, and UV spectroscopies. The confinement effect of longitudinal optical (LO) phonons in CdS quantum dots was investigated by Raman spectroscopy. Surface vibrational modes of CdS quantum dots were observed in IR spectra. It was shown experimentally that the frequency of the surface vibrational modes depends on the properties of the surrounding media. An average size of CdS quantum dots of about 3–6.4 nm was obtained from the analysis of UV measurements. Received: 1 February 1999 / Accepted: 1 April 1999 / Published online: 19 May 1999     

基于太赫兹光谱的氨基酸检测

太赫兹是指频率从0.1到2.0 THz之间的远红外波。与傅里叶红外相比,太赫兹时域光谱能量低,信躁比高,并且无辐射损伤。氨基酸分子的低频振动模式(扭转,集体振动模式和氢键)处在 THz波段。氨基酸是一类重要的生物分子,是组成蛋白质最基本的物质。氨基酸分子以分子间氢键相互连接构成晶体。氨基酸在THz波段比在红外波段体现更多独特吸收特征。到目前为止,已经获得了20种氨基酸分子的太赫兹吸收谱,包括利用太赫兹技术对部分氨基酸的定量分析。氨基酸的太赫兹光谱研究,有利于深层次理解蛋白质/ DNA的低频振动模式及相关生物反应和活性。文章综述了20种氨基酸分子的太赫兹吸收光谱并建立了吸收光谱数据库。总结了太赫兹技术在氨基酸应用方面存在的问题,并对未来发展方向进行展望。     

Vibrational studies of spinel LixMn2O4 (0.3≤x≤1.0) cathodes

We report on the vibrational properties of spinel LiMn₂O₄ and its electrochemically delithiated forms Li_xMn₂O₄. Raman scattering and infrared absorption spectra have been studied as a function of the delithiation content in the wavenumber range 50–700 cm⁻¹. Results show that lithium ions can be extracted at room temperature to obtain Li_x[Mn₂]O₄ (0.3≤x≤1.0) without disrupting the [Mn₂]O₄ array. The normal modes of the spinel LiMn₂O₄ have been discussed in the O _h ⁷ symmetry and vibrations due to lithium ions with their oxygen neighbors have been identified at ca. 400 cm⁻¹. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996