A shifted‐excitation Raman difference spectroscopy (SERDS) evaluation strategy for the efficient isolation of Raman spectra from extreme fluorescence interference

A biochemical characterization of pathologies in biological tissue can be provided by Raman spectroscopy. Often, the raw spectrum is severely affected by fluorescence interference. We report and compare various spectra‐processing approaches required for the purification of Raman spectra from heavily fluorescence‐interfered raw spectra according to the shifted‐excitation Raman difference spectroscopy method. These approaches cover the entire spectra‐processing chain from the raw spectra to the purified Raman spectra. In detail, we compared (1) area normalization versus z‐score normalization, (2) direct reconstruction of the difference spectra versus reconstruction of zero‐centered difference spectra and (3) collective baseline correction of the reconstructed spectra versus piecewise baseline correction of the reconstructed spectra and, finally, (4) analyzed the influence of the shift of the excitation wavelength on the quality of the reconstructed spectra. Statistical analysis of the spectra showed that – in our experiments – the best results were obtained for the z‐score normalization before subtraction of the normalized spectra, followed by zero‐centering of the difference spectra before reconstruction and a piecewise baseline correction of the pure Raman spectra. With our equipment, a wavelength shift from 784 to 785 nm provided reconstructed spectra of best quality. The analyzed specimens were different tissue types of pigs, tissue from the oral cavity of humans and a model solution of dye dissolved in ethanol. © 2015 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd.     

熊果酸的Raman光谱和红外光谱结构特征比较

本文采用HRD2型双光栅单色仪测定了熊果酸的Raman光谱，得到熊果酸的特征Raman光谱结构，采用Philips 100型双光栅单色仪测定了熊果酸的IR光谱，得到熊果酸的特征IR光谱结构；解析了熊果酸的Raman光谱和IR光谱与其结构特征的关系，确定了熊果酸的Raman光谱的结构特征和官能团的归属，给出了熊果酸的两个基本骨架特征区域（A区：1386，1370，1363cm^-1，B区：1304，1269，1237cm^-1）；对熊甲酸的Raman光谱和IR光谱作了比较研究，指出Raman光谱具有比IR光谱更为丰富的结构信息的特征，并且，IR光谱的主要特征峰在Raman光谱中均有对应的谱峰；Raman光谱的谱峰形态清晰可变，使熊果酸的主要结构和官能团得到准确的分析和指认，与IR光谱一样，Raman光谱是天然药物解析的有效手段之一。     

The characteristic X-ray spectra of free atoms of metals

The article presents the results of a study of characteristic X-ray spectra of free atoms by means of a new simple technique. A pulsed electron beam was used for evaporation and to create inner-shell vacancies in free atoms of metals. The spectra were obtained with the help of an X-ray monochromator which allowed precise comparison between the free-atoms spectra and corresponding solid-state spectra. The shifts of the peaks were measured and found to be in the range Δλ/λ≈10⁻⁵–10⁻⁴. The K-, L- and M-series spectra were studied. A number of the free-atoms spectra revealed structure which was not resolved in the solid-state spectra and which is of interest for atomic structure calculation applications. This electron beam technique for the investigation of X-ray characteristic spectra of free atoms can be used for the refinement of X-ray wavelength standards.     

Accurate interband-energy measurements from Ellipsometric spectra

The optical constants of AlGaInP, AlGaInP (Si-doping) and AlGaInP (Mg-doping) grown by MOCVD were measured in the region of visible light at room temperature using null spectroscopic ellipsometry, then the dielectric function spectra were obtained. By numerical differentiation, the third-derivative spectra of the dielectric function for three samples were evaluated. Based on the third-derivative theory, it was proved that the third-derivative spectra were proportional to the electroreflectance (ER) spectra under the low-field modulation condition. Thus, the third-derivative spectra given by the ellipsometric spectra were directly related to the band structure of material. Analyzing the third-derivative spectra of the imaginary part of the dielectric function with the three-point method used in ER spectra, the E_g and E_g+Δ₀ values of three samples were gained accurately. The experimental results were in good agreement with those published.     

MgB2各向异性光学性质的第一性原理研究

使用密度泛函第一性原理研究了超导体MgB₂单晶各向异性的光学性质.在描述光学性质的基本理论和计算方法的基础上,计算了MgB₂的光电导谱、反射谱以及电子能量损失谱,并通过MgB₂的各个原子分解态密度图对所得到的反射谱和损失谱的各个谱峰做了详尽地分析.从光电导谱上来看,x方向与z方向有着很大差别,而在反射谱与电子能量损失谱中,x方向与z方向的特征峰位置都是相互符合的.从光导谱来看,沿 关键词： 超导体 电子结构 光学性质     

Antiresonant dielectric spectra: Theory and experiment

It is established that, in ceramics based on solid solutions of BiFeO₃–SrTiO₃ and BiFeO₃–BaTiO₃ multiferroics, antiresonant dielectric spectra—a kind of spectra not described in literature—are possible in addition to relaxation and resonant spectra. Antiresonant dielectric spectra are simulated, and experimental data confirming the simulation results are obtained. It is shown that the antiresonant spectra are characterized by a large activation energy (U > 1 eV). A relationship between the antiresonant spectra and hopping conductivity is supposed.     

飞秒激光低压N2等离子体特性的实验研究

在低于一个标准大气压的条件下对飞秒激光产生的N₂等离子体光谱进行了实验研究.结果表明, 各种样品气压下的激光N₂等离子体光谱均表现为连续谱和线状谱的叠加.随着样品气压的降低, 连续谱和原子谱线的强度经历了由缓慢增强发展为缓慢降低再到迅速降低的过程, 而正一价离子谱线强度呈现逐步增强的特征.在气压低于0.3 atm (1 atm=101325 Pa)时, 出现了正二价态的离子谱线. 给出了低压N₂等离子体对于飞秒激光传输和能量吸收的物理特性, 并初步讨论了低压等离子体通道特性.这些结果有助于加深了解飞秒激光等离子体的特性和机理, 特别是给出了在实验上测量不同价态离子光谱的条件, 为今后的研究提供了有益的实验依据. 关键词： 飞秒激光 气压 等离子体光谱 激光传输     

Incoherent inelastic neutron scattering from hexamethylene-tetramine and adamantane

The incoherent inelastic neutron scattering spectra of hexamethylene tetramine (HMT) and adamantane have been measured at high resolution between 200 and 1000 cm^-1. The agreement between the frequencies of the observed spectra and the optical spectra of Mecke and Spieseche (HMT) and Bailey (adamantane) is good. The observed neutron spectra are also matched very closely by the calculated one-phonon spectra, computed from a normal-coordinate analysis. There is some additional structure in the neutron spectra which appears to be due to multiphonon scattering involving lattice modes.     

Low temperature electron energy loss spectra of acetylene chemisorbed on metal single-crystal surfaces; Cu(111), Ni(110) and Pd(110)

Vibrational spectra of acetylene chemisorbed on Cu(111), Ni(110) and Pd(110) at 110–120 K were measured using electron energy loss spectroscopy. Loss peaks were assigned to vibrational modes of the non-dissociatively adsorbed molecules with the aid of the corresponding C₂D₂ spectra. The spectra show that the molecules undergo significant rehybridisation on adsorption. Comparisons are made with the spectra of acetylene adsorbed on a range of other transition metal surfaces at low temperature. Taking into account these and earlier literature results, two distinct patterns of spectra are observed (Type A and Type B) for specular spectra. The Cu(111) spectrum is classified as Type A while the Ni(110) and Pd(110) spectra are classified as Type B. Suggestions are made for the structures of the surface species corresponding to the two spectral types.     

Anomalous infrared and visible light absorption and local structure of Ag–Au core/shell nanoparticles

We measured infrared and visible light absorption spectra and EXAFS for Ag–Au core/shell particles. The shell thickness and core diameter can be evaluated from the EXAFS results, which are almost consistent with those obtained using TEM. The influence of a thinner shell only slightly appeared in the visible absorption spectra, whereas the influence appeared strongly in the infrared absorption spectra. The spectra of the material in the vicinity of the particle surface appear in the infrared spectra. On the other hand, the spectra of the rather more internal material are observed in the visible spectra. It is thought that the influence of the core metal is different in the visible spectra from the infrared spectra. By considering the penetration depth, this phenomenon can be explained.     

Relation between 2p X-ray photoelectron and Kα X-ray emission spectra of manganese and iron oxides

The high resolution Mn and Fe Kα X-ray emission spectra (XES), and Mn and Fe 2p X-ray photoelectron spectra (XPS) for manganese and iron oxides were measured. The spectra were compared with those of [MnO₄]⁻, [Fe(CN)₆]⁴⁻ and [Fe(CN)₆]³⁻ ions. As the electronic structure of the latter compounds do not change with electron hole creation in the core levels, satellite peaks due to charge transfer are not observed in the 2p XPS spectra, and the peak profiles of metal 2p XPS and Kα XES are governed by the exchange splitting between 2p and valence electrons. The metal 2p XPS spectra of the oxides had satellite peaks, but the XES spectra had no satellites. FWHMs of the metal 2p_3/2 main peaks of the compounds being low spin states are smaller than those of metal Kα₁ XES spectra. However, FWHMs of Mn 2p_3/2 of the manganese oxide were nearly equal to those of Mn Kα₁ XES spectra, and those of Fe 2p_3/2 XPS spectra of the iron oxides are greater than those of Fe Kα₁ XES spectra.     

Comparison of the Raman spectra of superionic conductors AgI and RbAg4I5

The Raman spectra of superionic conductors AgI and RbAg₄I₅ have been measured in both cation disordered and normal phases. Similarities in the observed spectra of these two materials are discussed. The frequency dependent conductivity is obtained from the spectra and compared to infrared results. Several possible interpretations of the observed spectra are considered.     

Investigations of oxide superconductors by x-ray absorption,photoemission and cognate spectroscopies

X-ray absorption spectra, X-ray photoelectron spectra and Auger spectra of cuprate superconductors are discussed. The studies establish the absence of Cu³⁺ for all practical purposes, but point out the importance of oxygen holes. X-ray photoelectron spectra of BaBi_0.25Pb_0.75O₃ and related compounds are also examined.     

Magneto-optical properties of [Li]0 defects in MgO

Magnetic circular dichroism and optical absorption spectra are reported for MgO crystals containing [Li]⁰ defects. The spectra are identified by optical detection of the [Li]⁰ ground-state paramagnetic resonance spectrum. The spectra are interpreted for both the ion and polaron models of the defect. Either model gives a qualitative interpretation of the spectra, but neither gives quantitative agreement.     

Interpretation of the vibrational spectra of polycrystalline adenine

The infrared and Raman spectra of the tetramer of the adenine N₉H are calculated and analyzed. The vibrational spectra of polycrystalline adenine are interpreted. It is demonstrated that the method for calculating the vibrational spectra of molecular complexes formed by hydrogen bonds can be used for interpreting the vibrational spectra of polyatomic molecules in the solid state.     

New method for the restoration of the continuous distribution function of hyperfine fields andits possibilities

A mathematical approach for the evaluation of hyperfine field distribution functions based on an analytical approximation of Mössbauer spectra was developed. The calculations were performed for different model spectra andfor the experimental spectra of crystalline andamorphous alloys. It was possible to obtain an adequate interpretation of complicated Mössbauer spectra of multicomponent heterophase amorpho-crystalline alloys of the Nd-Fe-B-type.     

Electronic structure of strontium titanate

The spectra of three sets of optical functions for SrTiO₃ crystals are determined in a broad energy range of fundamental absorption. The calculations are carried out using the experimental reflectivity spectrum in the range 1–35 eV and two theoretical permittivity spectra in the ranges 0–30 eV and 0–14 eV. The special features of these spectra have been determined. The theoretical spectra of the optical functions are compared with the spectra determined using the experimental reflectivity spectrum.     

Diffuse Reflectance Spectra of Some Nd3+ Complexes: Bonding

The absorption spectra of Na³⁺ complexes have been a subject of several recent investigations.^1–7 In the absorption spectra of solutions, the solvent effect makes it difficult to study the energy levels of the complexes. This difficulty can be overcome by studying the absorption spectra of single crystals or diffuse reflectance spectra of powders. Since the complexes under study do not form good single crystals, it was thought worthwhile to study their diffuse reflectance spectra, which have not been studied so far. The present communication reports a comparative study of bonding in six complexes inferred from their diffuse reflectance spectra.     

两模腔场谱间的量子干涉

研究了高Q腔中单个二能级原子与两模二项式光场依赖强度耦合相互作用系统的腔场谱,给出了弱初始场条件下的数值结果,讨论了两模光场之间的量子干涉对腔场谱结构的影响. 发现当两模光场的频率差Δ>g（g为原子与腔场间的耦合常数）时,两模光场间的干涉效应对谱结构没有影响,系统的腔肠谱只是两模腔肠谱的简单叠加;当Δ≤g时两模腔场谱间的干涉比较明显. 在强初始场条件下,量子干涉效应可忽略. 关键词： 腔场谱 量子干涉 两模二项式光场     

Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron‐based K‐edge XANES spectroscopy

Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K‐edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free‐ and cation‐bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K‐edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated soil organic matter (SOM), but far less efficiently by hematite, Ca‐saturated montmorillonite and Ca‐saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K‐edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated SOM differ from each other. They also are different from the spectra of amorphous FePO₄, amorphous or crystalline AlPO₄, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P‐retaining soil minerals in addition to spectra of free or cation‐bound IHP, AlPO₄, FePO₄ and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K‐edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented.