Microwave spectra of HPO and DPO: molecular structure

Microwave spectra of the unstable phosphorus containing molecule, HPO, and its deuterated species were measured in the frequency range of 70-380 GHz. The molecule was produced by a DC-glow discharge of a gas mixture of PH₃, CO₂, and H₂(D₂). Rotational constants and centrifugal distortion constants for HPO and DPO were determined accurately. Harmonic force constants were evaluated from the centrifugal distortion constants determined in the present study, and with vibrational frequencies reported previously. The zero-point average structure for HPO was obtained by taking the isotopic difference of the PH bond length into consideration: r_z(PH)=1.473(7) Å, r_z(PO)=1.4843(9) Å, and θ_z=104.57(16)°. The errors were estimated from the residual inertial defect. Equilibrium bond lengths for the PH and PO bonds were derived as 1.455(7) and 1.4800(9) Å, respectively, by assuming anharmonic constants of the corresponding diatomic molecules.     

Microwave spectra and structure of an isoxazole-water complex

The rotational spectrum of a hydrogen-bonded isoxazole-water complex has been measured between 6–18 GHz with a pulsed nozzle Fourier transform microwave spectrometer. In addition to isoxazole-H₂O, the complexes with HDO and D₂O as well as isoxazole-¹⁵ N-H₂O have been investigated in order to determine the structure of the complex. Rotational constants, quartic centrifugal distortion constants and quadrupole coupling constants, where applicable, have been fitted to the measured transition frequencies of the isotopomers. Structural data, which have been deduced from the planar moments of inertia and the quadrupole coupling constants of the isotopomers, have established conclusively that water binds to nitrogen in the ring plane of isoxazole. Ab initio calculations have revealed that complexes with a hydrogen-bond to nitrogen or to oxygen are both stable. The complex with water attached to nitrogen has been found to be more strongly bound than that with water attached to oxygen. Small splittings of the rotational transitions of the two complexes with H₂O have been interpreted as being the result of an internal rotation of water with respect to isoxazole.     

Raman spectra and structure of a 25mer HCV RNA

We have employed Raman spectroscopy to investigate the conformation of an (Hepatitis C virus) HCV RNA 25mer (1–25 nucleotides) in solution. The principal findings of this study are (1) the A‐form secondary structure involving C3′‐ endo/anti ribofuranose pucker is predominant; (2) some uridine and guanosine nucleoside residues adopt the C2′‐ endo/anti and C3′‐ endo/syn conformations, respectively, which appear in looped nucleotide sequences; and (3) six out of nine guanine residues are base‐paired probably forming a stem. These results are interpreted as formation of a hairpin whose secondary structure is consistent with that proposed on the basis of phylogenetic comparisons with other viral RNAs. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectra and structure of small ring compounds. Microwave spectrum of cyanocyclobutane

The rotational spectrum of cyanocyclobutane has been investigated in the region 18.0–40.0 GHz. Only A-type transitions were observed. R-branch assignments have been made for the ground state and the first three excited states of the ring puckering mode as well as the first two excited states of the out-of-plane cyano-bending mode. The microwave data are consistent with a bent equilibrium ground state for the ring with the cyano-group in the equatorial position. The dipole moment components were determined to be μ_a = 4.04 ± 0.09 D and μ_c = 0.92 ± 0.03 D with the total dipole moment, μ, having a value of 4.14 ± 0.09 D.     

Raman spectra and thermal disordering of the crystalline structure of benzene

Disordering of rotational degrees of freedom of molecules in a benzene crystal is investigated from Raman spectra. Nonuniform smearing of the spectrum of librational vibrations to the wing of the Rayleigh line is established. The changes observed are interpreted on the basis of calculations of frequencies, intensities, vibration modes, and barriers to molecular reorientations in the crystal by the method of atom-atom potentials. The line broadening in the spectrum of external vibrations by reorientations of molecules in the crystal as a function of their mode is analyzed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 394–400, May–June, 1999.     

Raman Spectra of Porphyrins

The spectroscopy of porphyrins has been developing rapidly during the last two decades, this class of compounds being of great biological importance and possessing a number of significant properties. Different spectroscopic techniques, viz., electronic spectroscopy including fine-structure quasiline spectra (Shpolsky effect), infrared spectroscopy, luminescence, flash photolysis, ESR and NMR spectroscopy etc., have been applied to the study of these molecules (see reference ¹ for a review). However until recently there were no publications on Raman spectra of porphyrins and related compounds although it is evident that a complete analysis of molecular vibrations is impossible without knowing the Raman frequencies, especially for centrosymmetrical molecules. We have obtained Raman spectra of two porphin derivatives, viz., copper and nickel octamethylporphin ² which seems to be, together with data on hemoglobin and cytochrome^3-5 and on chlorophylls ⁶, the first observation of Raman spectra of porphyrins. In this paper Raman spectra of several metalloporphyrins are presented including metal complexes of porphin, octamethylporphin, etioporphyrin I, meso-tetraphenylporphin and tetrabenzporphin. For some of them Shpolsky spectra have been obtained and a juxtaposition is made of the two kinds of spectral data concerning the frequencies of molecular no- modss. Also some data of infrared spectra are presented.     

辉石的拉曼光谱

由拉曼光谱仪测试巨晶普通辉石及包体中的顽火辉石、透辉石拉曼光谱,描述了谱图的位置、形态和相对强度,分析了振动模式,同时对相应的离子基团如非桥氧Si—O—,桥氧Si—O0,O—Si—O,M—O做了谱带归属。通过不同切片方向的谱带强度相对大小及某些谱带的缺失,初步研究了辉石族矿物晶体结晶学定向问题。     

紫膜菌紫质的拉曼光谱测试

菌紫质是一种可进行光信息存储与能量转换的生物膜蛋白分子。在光化学循环中 ,它包含的视黄醛产生快速的全反——— 1 3顺式异构化并去质子 ,然后又重新质子化并在反应循环终了转为全反式构型。了解菌紫质的分子构造及光化学反应机制是很有意义的事 ,但由于菌紫质是紫色膜蛋白 ,加之光反应时的荧光问题 ,用普通拉曼技术获得菌紫质的特征峰有一定困难。一般都用时间分辨付里叶变换红外光谱来进行它的测试工作。文本采用传统拉曼技术 ,分别用 5 3 2、785和 1 0 64nm波长激光作激发光源 ,测试了菌紫质的拉曼光谱 ,并得到了菌紫质的大部分特征拉曼谱带。     

Tb掺杂的硅铝酸盐的拉曼光谱及其荧光光谱研究

采用高温固相法制备不同浓度Tb元素掺杂的硅铝酸盐荧光材料。当烧结温度为1 350 ℃时其荧光强度达到最大值。通过X射线衍射图谱可知体系中基质材料为CaAl₂Si₂O₈,Tb元素以Ca₂Tb₈(SiO₄)₆O₂相存在。通过拉曼光谱分析可知,870 cm-1处振动峰与Ca₂Tb₈(SiO₄)₆O₂中Tb与硅氧四面体的伸缩振动相关;Tb原子与硅氧四面体之间的弯曲振动产生408 cm-1振动峰。随着Tb掺杂量的增加,拉曼振动峰强度,荧光分光光度计测得的荧光光谱以及拉曼光谱仪测得的光致发光光谱的峰强均呈现先增后减的变化规律。该体系中Tb元素与硅氧四面体匹配数量逐渐增加,当Tb掺杂量超过一定极限值时,体系内发生浓度猝灭,导致荧光性能下降。采用325 nm激光作为激发光源,用拉曼光谱仪的光致发光测量模式产生的峰形与传统荧光分光光度计的光谱曲线一致,但其光谱分辨率明显高于传统荧光分光光度计获得的光谱,有助于对细微能级跃迁现象加以区分。     

Automatic Analysis of Raman Spectra

In this paper the automatic analysis of Raman spectra is described. The method applied is so-called SRIP, i.e. “Standard Representation Independent Parameter” fitting, which has been given previosly and proven to be steadily converging, if the model has been chosen properly. The approach is extended here by introducing the interactive continuation of the analysis: some of peaks may be rejected or left in the model with fixed up parameters of the position and full width at half maximum.

The main improvements of the algorithm is to be applied to the Raman spectra analysis include the mixed mathematical model as well as the enhanced sensitivity in discovering of peaks. That is achieved by the analysis of smoothed residuals at the steps of the peak revelation.

This approach enables successful analysis of spectra with low signal to noise ratio, without limitation in number of the peaks. The reliability of Raman band analysis was proven using overlapped spectra of solution of noninteracting liquids: carbontetrachloride (CTC), dichloromethane (DCM) and 1,2 dichloroethane (DCE) with different molar ratio. Solution spectra can be calculated from component spectra and compared with analysis by described method.     

Microwave spectra and structure of the fluorobenzene-carbon monoxide van der Waals complex

The rotational spectra of the fluorobenzene–CO complex and four of its isotopomers have been measured between 5–18GHz with a pulsed nozzle Fourier transform microwave spectrometer. An analysis with a rigid asymmetric rotor model revealed that CO must be located above the ring plane with CO at an angle to the symmetry plane. A second set of transitions indicated that CO is executing large amplitude motions. The rotational transitions of two states were analysed simultaneously using an effective model Hamiltonian which accounts for an internal rotation between CO and fluorobenzene hindered by a low barrier (below 25cm^-1).     

正交晶系PbO的拉曼光谱研究

在常温下对正交晶系一氧化铅(PbO)进行XRD测试,确定样品的晶格参数。利用1064nm的激发波长对样品进行拉曼测试,确认342cm-1是正交系PbO的拉曼信号。排除测量系统的噪声影响,得到了正交系PbO的全部12个拉曼峰。     

木糖醇的红外光谱和拉曼光谱研究

实验测量了木糖醇的拉曼光谱和红外光谱,在相关文献的帮助下,对其谱带进行了初步指认。在拉曼光谱中,1000cm-1～1110cm-1之间的中等强度振动属于C-O伸缩振动和H-C-O弯曲振动。850cm-1到920cm-1之间的振动属于C-C伸缩振动。羟基面内弯曲振动在红外吸收光谱中出现在1300～1500cm-1,O-H的变形振动δO-H出现在1420～1380cm-1。     

钛氧化物结构及其拉曼光谱表征

采用密度泛函理论(DFT),对几种钛的氧化物晶体结构进行了几何构型优化,得到了与X-ray晶体衍射实验结果相一致的结构参数。在优化几何构型基础上进行了分子振动模的分析和计算,钛氧化物均采用数字化基组和局域密度近似,并选择vwn对局域交换相关能量参数化,使用自旋非限制函数。同时,测定了钛的氧化物(TiO, Ti₂O₃,Ti₃O₅,锐钛矿型TiO₂和金红石型TiO₂)几种晶体的拉曼光谱,并分别解释了相关的拉曼活性振动模。结果表明：计算的频率与实验结果比较一致,理论计算频率可以指导实验谱图谱峰位置的归属分析。通过钛的一系列氧化物的常温拉曼光谱分析, 得知不同氧化物有不同特征峰,有利于含钛氧化物材料类型的诊断,为沟通结构和性能的相互关系奠定基础。     

Raman spectra of alcohols: Intensity measurements

The peak, integrated and standard intensities of some prominent Raman lines in twelve alcohols are estimated. The standard intensities of the lines due to some characteristic bonds in various alcohols are compared and large variations observed.     

铁镁明矾的拉曼和红外光谱

铁镁明矾的拉曼和红外光谱毛延哲，曾维杨（兰州大学物理系兰州７３００００）李万茂，李学军（兰州大学地质系兰州７３００００）ＲａｍａｎａｎｄＩｎｆｒａ－ｒｅｄＳｐｅｃｔｒａｏｆｔｈｅＦｅ－ｐｉｃｋｅｒｉｎｇｉｔｅ￥ＭａｏＹａｎｚｈｅａｎｄＺｅｎｇＷｅｉｙ...     

相互作用体系的极化率与拉曼光谱

分子的大多数光学性能取决于它的极化率和超极化率，例如折射率、旋光、Ｒａｙｌｅｉｇｈ和Ｒａｍａｎ散射、电光、磁光和非线性光学性能等［１］。分子间相互作用对于物质的性质有着深刻影响［２］，对于分子极化率及其有关的性能也是如此３］。本文在拉曼光谱强度理论（...     

质子辐照聚苯胺的Raman与红外光谱研究

本文用Raman与红外光谱表征质子辐照聚苯胺的结构。聚苯胺的红外光谱的主要吸收峰经低能和高能质子辐照后分别向高频移动2—12cm~(-1)和5—26cm~(-1)。在1228,1344,1380和1444cm~(-1)处的Raman带在低能质子辐照后分别移到1236,1348,1392和1456cm~(-1),在804,1588和1620cm~(-1)处的Raman带,经高能质子辐照后分别移到808,1592和1624cm~(-1)。醌型结构的拉曼线1588cm~(-1)也上移4cm~(-1)。这些结果表明,质子辐照不同于质子酸的掺杂(质子化过程)而是引起聚苯胺中分子链的断裂。