Automatic baseline correction of infrared spectra

A fast automatic algorithm is proposed for baseline correction of infrared (IR) spectral signals.It is devised based on iterative curve fitting where orthogonal polynomials are used.The algorithm can process both emission and absorption spectra automatically without human intervention.Orthogonal polynomials are used for curve fitting to reduce computation time.Both emission and absorption spectra are obtained and the results demonstrate the feasibility and practicability of this algorithm.     

Photoacoustic spectra studies of nanometer BaTiO_3

1IntroductionAtypicalpervoskitestypecompoundBariumTitanate(BaTiO3)isawideapplicabledi-electricmateria1withadvantagesashighdielectricconstantandspontaneouspolarization,etc.ItisalsoasemiconductorwithawidebandgaPof3.OoeVl1])intheforbiddenbandtheenergylevelactivitiesareverymoVable,sothatitattractedgreatattention.Intheeightiesthedevelopmelltofnanometer-scaledmaterialsopenedupanewfieldformaterialsciences.Nanometer-scaledmateriaJswithspecificcharacters,suchasthesmallgrain,bigsurfaceratioanddangli…     

Instantaneous coherent polarization and coherent polarimetric spectra

The statistics of polarization in electromagnetic waves or target vector has been studied deeply, generally using Stokes parameters. Unfortunately, all the data-processing includes the assumption that the sampling data are independent of time, without a consideration of the time coherence of the polarization data, such as instantaneous Stokes parameters. In this paper, the definitions of the instantaneous coherent polarization function and polarimetric spectrum are presented for the first time, which shows the coherences of the instantaneous Stokes parameters in both time and frequency domain, even in spatial coherence. The new formula of definition can be extended to spatial propagation coherence, both in free space or any linear medium.     

Beam-foil spectra of the highly ionized sulfur

Spectra of carbon, boron, beryllium, lithium, belium and hydrongen-line for sulfur obtained at an energy of 80 MeV, wherein thirty-four lines have been identified. Analysis of the spectra was based on theoretical results and other experimental data.     

Polarization-resolved Raman spectra of α-PtO_2

Using density functional theory,we investigate the vibrational properties and polarization-resolved Raman spectra ofα-PtO_2 and obtain the Raman tensor and angle-dependent Raman intensity of α-PtO_2.It is found that the polar plot of A_(1 g)mode in parallel polarization configuration is useful in identifying the orientation of the crystal.The Raman intensity of the Eg mode is about five times stronger than that of the A_(1 g) mode.The Raman intensity is about three times stronger when the wave vector of the incident light is in x or y direction than in z direction.Our work will help the material scientists to characterize the α-PtO_2 and to identify its orientation by comparing the experimental spectra with our result.     

The π-electron spectra of the benzene N-heterocyclics

The π-electron spectra of the nitrogen heterocyclics are discussed on the basis of a perturbation applied to the spectra of the corresponding aromatic hydrocarbons. The frequency of the first π→π band in pyridine is the same as that of the corresponding band in benzene, because of the accidental cancellation of a first-order blue shift by a second-order red shift. The first-and second-order shifts are related to two perturbation parameters, and these are obtained from experiment by examining the spectra of the benzene heterocyclics. These parameters can then be satisfactorily related to one another by assuming a perturbation field of the form exp (?2ηr)/r and by allowing for the C-N bond being shorter than the C-C bond in benzene.     

On the spectra of Schrödinger operators

We give two formulas for the lowest point in the spectrum of the Schrödinger operatorL=–(d/dt)p(d/dt)+q, where the coefficientsp andq are real-valued, bounded, uniformly continuous functions on the real line. We determine whether or not is an eigenvalue forL in terms of a set of probability measures on the maximal ideal space of theC ^*-algebra generated by the translations ofp andq.Research supported in part by the National Science Foundation under Grant DMS-910496     

Heavy-flavour spectra in high-energy nucleus–nucleus collisions

The propagation of the heavy quarks produced in relativistic nucleus–nucleus collisions at RHIC and LHC is studied within the framework of Langevin dynamics in the background of an expanding deconfined medium described by ideal and viscous hydrodynamics. The transport coefficients entering into the relativistic Langevin equation are evaluated by matching the hard-thermal-loop result for soft collisions with a perturbative QCD calculation for hard scatterings. The heavy-quark spectra thus obtained are employed to compute the differential cross sections, the nuclear modification factors R _AA and the elliptic-flow coefficients v ₂ of electrons from heavy-flavor decay.     

Spreadsheet based analysis of Mössbauer spectra

Using spreadsheet programs to analyse spectral data opens up new possibilities in data analysis. The spreadsheet program contains all the functionality needed for graphical support, fitting and post processing of the results. Unconventional restrictions between fitting parameters can be set up freely, and simultaneous analysis i.e. analysis of many spectra simultaneously in terms of model parameters is straightforward. The free program package Vinda – used for analysing Mössbauer spectra – is described. The package contains support for reading data, calibration, and common functions of particular importance for Mössbauer spectroscopy (f-factors, second order Doppler shift etc.). Methods to create spectral series and support for error analysis is included. Different types of fitting models are included, ranging from simple Lorentzian models to complex distribution models.     

Ghost lines in Mössbauer relaxation spectra

The appearance in Mössbauer relaxation spectra of ghost lines, which are narrow lines that do not correspond to transitions between real hyperfine energy levels of the resonant system, is examined. It is shown that in many cases of interest, the appearance of these ghost lines can be interpreted in terms of the relaxational averaging of one or more of the static interactions of the ion.     

Recurrence spectra of Li atom in strong external fields

Based upon our previous work [Commun. Theor. Phys.. 40,702 (2003)], we developed the closed orbit theory from two degrees of freedom to three non-separable degrees of freedom and calculated the recurrence spectra of Li Rydberg atom in strong perpendicular electric and magnetic fields. The Fourier transformed spectra of Li atom has allowed direct comparison between the resonance peaks and the scaled action values of closed orbits, whereas the nonhydrogenic resonance can be explained in terms of the new orbits created by the core scattering. The semiclassical result is in good agreement with the quantum one, which suggests that our calculation is correct.     

μSR frequency spectra using the maximum entropy method

A novel approach to extracting frequency spectra from transverseSR spectra is presented, based on the maximum entropy method. This has the advantages of ensuring positivity of the frequency spectra, and only deviating from a flat default level where there is statistically significant information present in the data. It allows simultaneous analysis of spectra from multiple detectors with different phases to yield a single frequency spectrum.     

Magnetic field effects on Mössbauer spectra ofAuFe

Zero and applied field Mössbauer spectra onAuFe alloys with 5, 10 and 20 at % Fe have provided information on the spin glass, cluster glass and long range ferromagnetic phases which are present in this system. The mean hyperfine parameters for these phases are presented.     

Approximation of Mössbauer spectra of metallic glasses

Mössbauer spectra of iron-rich metallic glasses are approximated by means of six broadened lines which have line position relations similar to those of -Fe. It was shown via the results of the DISPA lineshape analysis that each spectral peak is broadened owing to a sum of Lorentzian lines weighted by a Gaussian distribution in the peak position. This paper presents the Mössbauer parameters of amorphous metallic Fe₈₃B₁₇ and Fe₄₀Ni₄₀B₂₀ alloys derived from the fitted spectra.We would like to thank Dr. P. Duhaj for the preparation of amorphous samples.     

Microstructure and Raman spectra of Ag-MgF_2 cermet films

Ag-MgF2 cermet films with different Ag fractions were prepared by vacuum evaporation. The micfostruc-ture of the films was examined by Raman scattering technique. The surface-enhanced Raman spectrum for MgF2 molecules in the cermet film strongly suggests the existence of Ag nanoparticles dispersed in MgFa matrix. The intensities of the Raman spectra of Ag-MgF2 cermet films increase with Ag fraction. The enhancement of Raman scattering disappears when Ag content reaches wt.20%. The analyses with the transmission electron microscopy showed that Ag-MgF2 cermet films are mainly composed of amorphous MgF2 matrix with embedded faced-center-cubic Ag nanoparticles. It suggests that the percolation threshold should be around wt.20% of Ag content.     

EPR spectra of γ-irradiated hydrated barium dithionate single crystals

EPR spectra of barium dithionate hydrate single crystals γ-irradiated at low (80 Gy) and high (10 kGy) doses are studied. Four lines, the strongest of which is due to the SO₃⁻ radical, are observed in the EPR spectrum of the low-irradiated samples. Another line seems to belong to SO₂⁻. The strong line and weak lines with hyperfine structure and lines for pairs of closely spaced SO₃⁻ centers with a strong angular dependence are observed at high irradiation doses. The main values of the SO₃⁻ hyperfine coupling tensor and the dipole-dipole coupling constants of the SO₃⁻ pairs are determined. A quantum-chemical calculation of the electronic structure of isolated SO₃⁻ and SO₂⁻ radicals is performed. Values of the g tensors and hyperfine couplings are calculated. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 18–22, January–February, 2008.     

Radiofrequency mössbauer forward scattering spectra in magnetic materials

Radiofrequency (RF) Mössbauer spectra in experiments on forward scattering by thick samples of iron borate (FeBO₃) below the Neel temperature are measured. The spectra have satellites spaced by doubled RF-field frequency. A semiclassical model of Mössbauer transmission through a magnetic absorber exposed to RF reversals of a hyperfine field on nuclei is proposed. The model reproduces all features of the measured spectra. Experiments and modeling calculations indicate additional possibilities for studying soft magnetic materials using this measurement scheme.