The influence of electron scattering on the lineshape of auger and photoelectron spectra

A simplified model of Auger and photoelectron scattering in solids is presented. Within the framework of the model the relation between the distribution of backscattered primary electrons and Auger photoelectron distribution is obtained in terms of the geometric factor and the density of inelastic electron scattering probability. The new algorithm of spectrum background subtraction is formulated and applied to process the X-ray photoelectron and Auger spectra for a series of oxygen, fluorine, and copper compounds. It is shown that the method accuracy for the peak area measurements is better than 10%.     

Secondary and auger electron spectra of a Cu-Be alloy

The slow secondary electron spectra corresponding to the copper rich surface and oxidized beryllium surface of Cu-Be alloys are observed after argon ion bombardment and heating treatment of the sample and they are identified by Auger electron spectroscopy.     

Deconvolution of loss features from electron spectra

The problem of deconvoluting loss features from energy spectra of electrons emitted from solids is investigated. A new formula is found for the case of an exponentially decreasing intensity from the solid surface of electron emitters. This as well as a formula for the case of a homogeneous distribution of electron emitters is studied in detail. Central in the formulas is the cross section for inelastic scattering. Under the assumption that angular deflection of electrons can be ignored the formulas are exact, i.e. the effect of all multiple scattering events is included. Through numerical calculations on Al spectra the effect of deconvolution is tested, and it is demonstrated that a small deviation from the exact procedure can result in spurious structure in the deconvoluted spectrum.     

Fully automatic software correction of fourier transform NMR spectra

A simple computational procedure is discussed by which it is possible to correct fourier NMR spectra automatically for all amplitude and phase distortions resulting from signal-conditioning circuits and from anomalies in quadrature phase detection.     

Correction of baseline and lineshape distortions in fourier transform NMR spectroscopy by estimation of missing signals

Lineshape distortions and baseline undulations are the well-known undesirable effects of the linear phase correction, when applied to signals the initial part of which is corrupted, either duplicated or missing. While the former imperfection can be cured easily by proper time setting, the latter is more principal. It is shown, however, that some general prior knowledge of spectra enables the reconstruction of the missing part of the signal with high fidelity and the removal of most of the distortions appearing in the absorption-mode spectra. For this purpose a simple procedure is proposed yielding good results even after a single iteration step. Simplicity, negligible computational requirements, and its efficacy are the main advantages of this method.     

Applications of near-infrared spectroscopy to process analysis using fourier transform spectrometer

The applications of near-IR spectroscopy to process analysis using a Fourier transform spectrometer are described. In recent years, process analysis based on near-IR spectroscopy has received keen interest from a growing number of industries. Some configurations of Fourier transform near infrared (FT-NIR) interferometers used for process analysis are introduced as special optical systems for the realization of stable and reproducible performance. Moreover, the applications of NIR spectroscopy to process analysis using FT-NIR spectrometers are overviewed and two examples of applications are described in more detail. Furthermore, process analytical technology (PAT) for the pharmaceutical industry is introduced as a future trend of the application of FT-NIR spectroscopy, and a dual-wavelength system that can combine NIR and IR spectra is discussed as a newly proposed PAT tool for understanding processes.     

High-resolution infrared spectra of air pollutants with fourier transform spectroscopy

A Fourier transform spectrometer coupled with a long-path cell was used to record high resolution infrared spectra of air pollutants at very low concentrations. The spectral transmittance curves of CO were measured at room temperature, at a constant resolution of 0·5 cm^-1, at partial pressures from 2·32 to 0·004 torr, N₂ being the diluent. Apparent absorption coefficients were tabulated at 0·2-cm^-1 intervals. The techniques and data are applicable to studies of our contaminated atmosphere.     

Edge-enhancement fourier transform X-ray microscopy using a Laguerre-Gaussian zoneplate

Efficient techniques to achieve isotropic edge enhancement in optics involve applying a radial Hilbert, Laguerre-Gaussian, or differentiating filter on the object spectrum. We demonstrate a simple setup for isotropic edge-enhancement in soft-X-ray microscopy, using a single Laguerre-Gaussian zone plate (LGZP). Since the LGZP acts as a beam-splitter, diffraction efficiency problems usually associated with X-ray microscopy optics are not present in this system. As numerically demonstrated, the setup can detect optical path differences as small as λ/50 with high contrast.     

The use of the fast fourier transform in high resolution spectroscopy

Journal of Applied Spectroscopy -     

Energy loss spectra,auger spectra and high energy electron diffraction of A-15 superconductors

We have measured the electron energy loss spectra of V₃Si, Nb₃Al, Nb₃Sn, Nb₃Ge (annealed) and Nb₃Ge (sputtered) from 3 to 70 eV. Numerous new structures were discovered in this study which could be related to interband transitions, plasma excitations, and core transitions. We have also measured the high energy electron diffraction patterns and Auger spectra which characterized the lattice structures and compositions of these surfaces.     

Semi-empirical elemental sensitivities for quantitative auger electron spectroscopic analysis

A semi-empirical equation is presented which may be used to calculate the relative sensitivities of the elements for Auger electron spectroscopic analysis. The equation involves the product of a large number of theoretically or empirically derived terms, including ionization cross section. Coster—Kronig transitions, backscattered electron contribution, individual Auger transition probabilities, atomic density, electron mean free path, analyser transmission, modulation effects, detector efficiency, and peak asymmetry. The calculated sensitivities are compared with experimental relative elemental sensitivities from the Handbook of Auger Electron Spectroscopy. The close agreement obtained with experiment suggests that the semi-empirical theory is now capable of providing elemental sensitivities for analysis, in a predictive way, where reliable empirical sensitivities are missing.     

Application of Measurement multiple-image fourier of fast phenomena transform spectral imaging to measurement of fast phenomena

A new interferometric technique that simultaneously acquires all optical data necessary to reconstruct a spectral image is proposed. The optical data is a two-dimensional array 0L two-dimensional interference patterns. The data are acquired by an optical system consisting of a two-dimensional lens array and a Michelson interferometer. The interference patterns are generally distorted by the errors in path differences. These errors can be estimated beL0rehand and corrected in the process of reconstruction of the spectral image. Experimental results obtained with this technique applied to a fast phenomenon are also presented.     

Observation of resonance recombination lines in electron excited auger spectra of Gd

Combined measurements of electron excited N_4,5 Auger spectra and photoelectron emission on clean and oxidized Gd lead to a distinction between Auger lines originating from 4d → continuum and 4d → 4? resonance excitations. Several Auger structures are identified as due to the direct recombination of 4d⁹4?⁸ states with the 4f and valence electrons. The shape of the most prominent Auger line for oxidized Gd agrees perfectly with the Fano profile of the 4? photoemission intensity.     

Some aspects of auger electron spectra of 3d transition metal oxides

Auger electron spectra of the transition metals Cr, Mn, Fe, Co and Ni as well as their oxides have been investigated in the energy range between 0–100 eV. In each case of the clean metal surface the observed spectrum consists essentially of one Auger line identified asM _2,3 VV transition. After oxidation a line doublet is observed revealing two transitions instead of one. Additional new Auger peaks appear in the low energy range between 0–30 eV. The “splitting” of the Auger line can be explained as resulting from aM _2,3 V _dV_d and aM _2,3 V _pV_p transition. The latter is characteristic for the compound and can in a simple way be interpreted as a cross transition.     

Relations between chirp transform and Fresnel diffraction, Wigner distribution function and a fast algorithm for chirp transform

Two physical interpretations of chirp transform related to Fresnel diffraction and Wigner distribution function are given.The chirp transform can be regarded as a Fresnel diffraction observed on a spherical tangent to the diffraction plane,or a rotation and stretching transformation of the Wigner distribution function space.A general fast algorithm for the numerical calculation of chirp transform is developed by employing two fast Fourier transform algorithms.The algorithm,by which a good evaluation can be achieved,unifies the calculations of Fresnel diffraction,arbitrary fractionalorder Fourier transforms and other scalar diffraction systems.The algorithm is used to calculate the Fourier transform of a Gaussian function and the Fourier transform,the Fresnel transform,the Fractional-order Fourier transforms of a rectangle function to evaluate the performance of this algorithm.The calculated results are in good agreement with the analytical results,both in the amplitude and phase.     

High resolution lmm auger electron spectra of some first row transition elements

Auger spectra have been recorded from elements of the first transition series using a hemispherical analyser. Highly resolved LMM spectra were obtained showing for the first time the composite nature of these peaks for many of the elements studied. The recorded spectra show a general similarity for the elements Sc → Zn but interesting differences emerge. At the beginning of the transition period the L₃ based transitions have the relative intensities L₃ M_2,3, M_2,3 > L₃ M_2,3, M_4,5<> L₃ M_4,5, M_4,5 whereas towards the end of the series the order L₃ M_4,5, M_4,5 > L₃ M_2,3, M_4,5<> L₃ M_2,3, M_2,3 is observed. Pronounced chemical shifts have been observed upon oxidation. The spectra are interpreted in terms of an L -S coupling scheme and the fine structure discussed in terms of effects produced by multiplet splitting.