A short recollection on the paper entitled "A common sense approach to peak picking in two-, three-, and four-dimensional spectra using automatic computer analysis of contour diagrams" by D.S. Garrett, R. Powers, A.M. Gronenborn, and G.M. Clore [J. Magn. Reson. 95 (1991) 214-220

The Contour Approach to Peak Picking was developed to aid in the analysis and interpretation and of multidimensional NMR spectra of large biomolecules. In essence, it comprises an interactive graphics software tool to computationally select resonance positions in heteronuclear, 3- and 4D spectra.     

滇龙胆紫外指纹图谱共有峰率和变异峰率双指标序列分析法

利用共有峰率和变异峰率双指标序列分析法,采用平均值、平滑和一次微分处理方法校准和排除干扰,提高光谱的分辨率,考察三种极性溶剂提取的滇龙胆样品中各波段稳定性和重现性的变异系数RSD,计算紫外指纹图谱共有峰率和变异峰率,对滇龙胆样品间进行定性评价.结果表明,滇龙胆在氯仿、无水乙醇和水三种极性溶剂下分别提取40 min可达到最大提取率,且稳定性在30 h内变异系数RSD%分别在0.078～0.455,0.158～0.462,0.052～0.682之间;重现性变异系数RSD%分别在0.044～0.753,0.156～0.288,0.191～2.413之间.指纹图谱显示,滇龙胆不同产区样品间最大共有峰率达67.6%,最小共有峰率为45.2%,变异峰率最大为78.9%,最小为21.7%.该法可以准确对两个以上中药材样品进行定性评价,阐明不同产区间的相似程度,为中药材真伪鉴定和品质评价奠定基础.     

A simple approach to the analysis of positron lifetime spectra

A new method is proposed to deal with analysis of positron annihilation lifetime spectra which defy ordinary computer fitting. The method is particularly suited for investigations of defects in metals.     

A new approach to analysis of reflection electron energy loss spectra

A new approach is proposed for the analysis of reflection electron energy loss (REEL) spectra that were obtained for different electron-scattering configurations. A distinctive feature of the approach is that a REEL spectrum can be separated into two components that change in relative intensity with changes in the experimental configuration. No assumption is made about the number of peaks in the component spectrum and their shape. The suggested method is demonstrated on REEL spectra of aluminium, which is a traditional test object. It is established that in the range of energy losses 0–50 eV, the A1 REEL spectrum can be described by the sum of two components. The components of the spectra measured at different angles of primary electron incidence and exit angles for the detected electrons but with constant scattering angle have the same shape. The relative intensities of the two components define the spectral shape for different geometric conditions of the experiment. The shape of the components and their changes in relative intensity with change of primary electron energy give new information useful for development and further improvement of models used for studying medium energy (0.1–1.0 keV) electron scattering in the surface region of solids.     

A unified approach to phase diagrams in field theory and statistical mechanics

We construct the phase diagram of any system which admits a low-temperature polymer or cluster expansion. Such an expansion turns the system into a hard-core interacting contour model with small, but not necessarily positive, activities. The method uses some of Zahradnik's ideas [Z1], but applies equally well to systems with complex interactions. We give two applications. First, to low-temperatureP()₂ models with complex couplings; and second, to a computation of asymptotics of partition functions in periodic volumes. If the index of a supersymmetric field theory is known, the second application would help determine the number of phases in infinite volume.Alfred P. Solan Research Fellow. Supported in part by the National Science Foundation under Grants PHY87-064220, DMS 88-58073, and PHY/DMS 86-45122     

Fluctuation theory of hydrogen bonding applied to vibration spectra of HOD molecules in liquid water. II. Infrared spectra: contour shape,integrated intensity,temperature dependence

The infrared spectra of HOD molecules in liquid water are calculated at constant density over the temperature range of 10 to 400°C from the statistical distributions of the vibration frequencies of water OH-groups determined previously from the experimental Raman spectra. Their shape and position are extrapolated over a wider temperature range. The dependence of contour shape and integrated intensity of the IR band on the frequency of its maximum, the first moment of a statistical contour and temperature are described numerically and analytically. Calculations are in qualitative agreement with all available experimental material and fitted quantitatively at a density of water of ～1?g?cm^?3. The success of the proposed model applied to infrared spectra supports once more the continuum treatment of liquid water structure.     

A new approach to describing the statistical laws governing the formation of the contour of individual bands in the optical absorption spectra of liquid systems

A new approach to the problem of a quantitative study of the statistical laws governing the formation of the contour of individual bands in the optical absorption spectra of unordered molecular systems (liquids, solutions, liquid crystals, etc.) was developed. The approach is based on a joint consideration of two independent mechanisms of the inhomogeneous broadening of spectral bands; these mechanisms are related to fluctuations of the isotropic and anisotropic components of the total interaction potential of a molecule with the surrounding medium. A generalized expression for the total statistical contour was derived, which made it possible to describe quantitatively the Q-band contour in the vibrational-rotational IR absorption spectrum of a HCl solution in CCl₄ at room temperature.     

A unified approach to long-range and short-range many-body corrections to optical spectra of semiconductors

Long-range Coloumb - and exchange interactions - leading to bound exciton states at the onset of the optical spectra of semiconductors and to Fano-type excitonic resonances in the continuum - and short-range Coulomb - and exchange interaction, that lead to a red shift in the low-energy part of the spectra as compared to one-particle calculations, are treated in a unified approach. Almost quantitative agreement between theoretical absorption spectra is obtained without any fitting parameter in the case of sc TlCl.     

Volume and conformation. A simple approach to the conformational analysis

The molecular volume of some polymers and linear molecules has been calculated as a function of the internal rotation angles around the non rigid bonds. The new method gives the same conclusions as derived from the calculation of the conformational potential energy. Therefore it seems that, in many cases, it is possible in a simple way to predict the more stable molecular conformations.     

A self-consistent approach for modelling the interfacial properties and phase diagrams of Yukawa,Lennard-Jones and square-well fluids

A self-consistent density-functional approach is presented for describing the phase behaviour and interfacial tensions of van der Waals fluids represented by the hard-core Yukawa (HCY), Lennard-Jones (LJ) and square-well (SW) potentials. The excess Helmholtz energy functional is formulated in terms of a modified fundamental measure theory (MFMT) for the short-ranged repulsion and a density-gradient expansion for the van der Waals attractions. Analytical expressions for the direct correlation functions of uniform fluids are utilized to take into account the effect of van der Waals’ attraction on intermolecular correlations. For bulk phases, the density functional theory is reduced to an equation of state (EOS) that provides accurate saturation pressures and vapour–liquid phase diagrams. Near the critical region, the long-range fluctuations can be corrected by using the renormalization group (RG) theory. With the same set of molecular parameters, the theory also yields satisfactory surface tensions and interfacial density profiles at all relevant temperatures.     

A comparative analysis of the mesoscale stress-strain state in two- and three-dimensional polycrystalline specimens

A comparative analysis has been performed of mesoscale stress and strain distributions in sections of 3D polycrystalline specimens and in their 2D cousins under plane strain and plane stress conditions. For similar macroscale stress-strain curves, the mesoscale plastic strain localization patterns are shown to differ essentially both qualitatively and quantitatively in 2D and 3D models. In other words, the same effective mechanical response of the materials can be provided by different mesoscale stress and strain distributions depending on the loading technique used and geometric features of the specimens (thin plates, thick specimens, etc.).     

A self-modeling approach to the resolution of XPS spectra into surface and bulk components

A method of resolving XPS spectra into surface and bulk component spectra for cases of moderate energy resolution is designed based on an analysis of a family of spectra acquired at different polar angles from flat specimens. Assumptions about line shapes are not required, but an analytical model of the angular dependence of the bulk and surface XPS signals is needed when the component spectra overlap in the range of binding energies of interest. Recommendations are made of the error limits of experimental variables for the successful application of the self-modeling method. The method was used successfully in the separation and quantitative analysis of the O(1s) XPS spectra of surface silanols from bulk silicon dioxide of a fully hydrated silicon dioxide surface. The surface (silanol) and bulk (oxide) components were found to be separated by 0.30 eV, and the surface component was found to be broader (1.58 eV) than the bulk component (1.15 eV).     

Curvilinear coordinates and the dushenskii relation in the theory of molecular spectra. A general approach

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 1, pp. 69–73, July, 1991.     

Local approach to polarizabilities and trends in the Raman spectra of semiconductors

The Raman spectra of several II-VI and III–V compounds are well described with one parameter, namely the ratio of non-linear intra-ionic polarizabilities of the individual ions. This approach is justified by the open-shell electronic configuration of the compounds and is based on a simple overlap shell model which reproduces the phonons in many binary compounds. The relations to bond polarizabilities and the anomalous case of oxides are discussed.     

Characterization of Au nano-cluster formation on and diffusion in polystyrene using XPS peak shape analysis

XPS peak shape analysis is used as a novel and nondestructive method to study Au nano-cluster growth mechanism on polystyrene (PS) as a function of deposition as well as diffusion and distribution of the nano-clusters in PS as a function of subsequent annealing at temperatures in the range from room temperature to above the glass transition temperature of PS. The Au nano-cluster size and density are determined for four different amounts of Au deposition. It is shown that this nondestructive method can give all mentioned information on such a metalized polymer without the need for any other complimentary and time consuming technique such as AFM, TEM and the destructive technique XTEM. Thus this method is suitable to monitor and control the degree of intermixing of metal nano-clusters and polymers which is of high technological interest.     

Calculation of kinetic energy terms for the vibrational Hamiltonian: Application to large-amplitude vibrations using one-, two-, and three-dimensional models

One-, two-, and three-dimensional models involving large-amplitude vibrations have been used to calculate kinetic energy terms. Principle G matrix elements as well as cross terms in the kinetic energy were determined. Calculations were done on models involving the ring-puckering and PH inversion vibrations for 3-phospholene and the ring-puckering, ring deformation, and SiH₂ in-phase rocking vibrations for 1,3-disilacyclobutane. Kinetic energy expansions for g₄₄ and g₄₅ type terms were determined. Calculations show a coordinate dependence of the principle G matrix elements as well as of the g₄₅ terms. The vectorial models used in these calculations make it possible to treat vibrations in a one-, two-, or three-dimensional model separate from the other vibrations without carrying out a coordinate transformation, which would be necessary for the Wilson GF high- or low-frequency separation.     

Study on molecular structure and vibrational spectra of 5,7-dimethoxycoumarin using DFT: A combined experimental and quantum chemical approach

Conformational analysis of 5,7-Dimethoxycoumarin was performed and two stable conformers were obtained. The difference between the total energies of these conformers was 1.4698 kcal/mol and the difference between the zero point corrected energies was nearly zero. Vibrational frequencies of these conformers were calculated by B3LYP method using 6-311++G(d, p) basis sets and compared with experimentally recorded FT-IR and Raman spectra. Vibrational assignments were made by calculated total energy distributions. Time dependent density functional theory calculations were done by the same level of theory in order to investigate low-lying excited state and obtained results were compared with the maximum absorbtion peak value of experimental UV-visible spectrum.