Resolution enhancement of x‐ray photoelectron spectra by maximum entropy deconvolution

Splinter, S.J.; McIntyre, N. S.

doi:10.1002/(sici)1096-9918(199803)26:3<195::aid-sia364>3.0.co;2-#

Cited by 31 publications

(12 citation statements)

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“…Furthermore, the noise of ARXPS data strongly affects the results. , The reconstruction is based on the assumption of model profiles but, due to the presence of noise, many models matching experimental data might exist. , For this reason, it is not possible to reconstruct the profiles by simply minimizing the weighted sum-of-square differences between calculated and measured data, especially if the surface layer is complex and consists of many components. However, the reconstruction of the depth profiles from ARXPS data is achievable by the maximum entropy method (MEM). ,− …”

Section: Introductionmentioning

confidence: 99%

Nanostructure of Surface Films on Ni18P Alloy in Sulfate Solutions by the Maximum Entropy Method

et al. 2017

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NiP alloys are very often used in industry, due to their outstanding performance in corrosion and wear. Alloys with high phosphorus content (≥16 atom % P) are amorphous and show high corrosion resistance in both neutral and acidic solutions irrespective of the presence of chloride ions. The reason for this behavior is attributed to the formation of a “P-enriched surface layer” whose exact nature is still under debate. In this work, an iterative algorithm based on the application of maximum entropy method on nondestructive angle-resolved X-ray photoelectron spectroscopy data has been applied to the investigation of the surface layer grown on Ni18P alloys following mechanical polishing and anodic polarization in sulfate solutions. The results show that the outermost region of the examined alloy has a complex layered structure: (1) an uppermost hydrocarbon contamination layer about 1 nm thick, which includes also adsorbed water; (2) a nickel (poly)phosphate layer of about 1 nm; (3) a highly phosphorus-enriched interface being about 2 nm thick with a marked phosphorus concentration gradient, from 70 to 20 atom %; and (4) bulk alloy with the stoichiometric composition. These findings, together with the chemical state of the different phosphorus compounds, allow us to conclude that the high corrosion and wear resistance of NiP alloys might be ascribed to the presence of a thin, self-repairing nickel (poly)phosphate layer grown on a strongly P-enriched interface. Because the Auger parameter of P at the interface is similar to that of elemental P, it might be also concluded that the interface is enriched in elemental phosphorus

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Section: Introductionmentioning

confidence: 99%

Nanostructure of Surface Films on Ni18P Alloy in Sulfate Solutions by the Maximum Entropy Method

et al. 2017

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“…Analytical inversion leads to an amplification of instrumental noise and a highly oscillatory behavior of w tot ( n ) with possibly negative values, lacking physical meaning. , Sophisticated numerical approaches therefore have to be used for the calculation of w tot ( n ). Maximum entropy methods − have successfully been applied in a number of related scientific problems in image reconstruction , spectroscopy and chromatography . We have therefore chosen this approach to calculate w tot by the procedure outlined in Figure (note the change in variable nomenclature, due to the fact that the procedure works with discrete data).…”

Section: Methodsmentioning

confidence: 99%

“…Combining both data sets to gain absolute molecular weight distributions free from band broadening requires a sophisticated data processing algorithm. Use was made of the so-called maximum entropy (MaxEnt) principle for this purpose, − as data from the present kind of experiment contain a great amount of redundancy, usually leading to amplification of noise in the restored MWDs. With the employed system, MWDs of low and high polydispersity standards with a molecular weight of up to 15 kg mol −1 corrected for chromatographic band broadening could successfully be determined …”

Section: Introductionmentioning

confidence: 99%

Fast and Accurate Determination of Absolute Individual Molecular Weight Distributions from Mixtures of Polymers via Size Exclusion Chromatography−Electrospray Ionization Mass Spectrometry

2009

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We present a method to determine accurate and absolute molecular weight distributions (MWDs) as well as absolute concentrations of the individual macromolecular components in mixtures of polymers of the same monomer class yet differing in their end groups. Data gained from size exclusion chromatography coupled online to refractive index (RI) detection and electrospray ionization mass spectrometry (ESI-MS) are processed by a sophisticated computer algorithm based on the maximum entropy principle. The procedure yields, for the first time, absolute molecular weight distributions of each component corrected for chromatographic band broadening. Molecular weights of up to 10 kDa are accessible with a conventional quadrupole ion-trap mass analyzer. The method is applicable to variable polymer systems regardless of the monomer class and without the need for an external calibration or additional model assumptions. It was validated using binary and ternary mixtures of poly(methyl methacrylate) carrying labile functional groups. For the ternary mixture, maximum deviations of the reconstructed molecular weight averages and mass concentrations from the original values were 8% and 5%, respectively.

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“…The purpose of regularization is then to produce an estimate or reconstruction x of x from m, or, where the effects of blurring are negligible or of no interest, a reconstruction of x * b from m. One such regularization method is TPMEM. 9 It has been used to modify the MEM 4,12,13 by replacing the negative entropy term in the cost function with a two-point negative entropy term such that the cost function, F TM , is given by…”

Section: Theorymentioning

confidence: 99%

Two-Point Maximum Entropy Noise Discrimination in Spectra over a Range of Baseline Offsets and Signal-to-Noise Ratios

et al. 2007

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The two-point maximum entropy method (TPMEM) is a useful method for signal-to-noise ratio enhancement and deconvolution of spectra, but its efficacy is limited under conditions of high background offsets. This means that spectra with high average background levels, regions with high background in spectra with varying background levels, and regions of high signal-to-noise ratios are smoothed less effectively than spectra or spectral regions without these conditions. We report here on the cause of this TPMEM limitation and on appropriate baseline estimation and removal procedures that effectively minimize the effects on regularization. We also present a comparative analysis of TPMEM and Savitzky-Golay filtering to facilitate selection of the best technique under a given range of conditions.

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Resolution enhancement of x‐ray photoelectron spectra by maximum entropy deconvolution

Cited by 31 publications

References 50 publications

Nanostructure of Surface Films on Ni18P Alloy in Sulfate Solutions by the Maximum Entropy Method

Nanostructure of Surface Films on Ni18P Alloy in Sulfate Solutions by the Maximum Entropy Method

Fast and Accurate Determination of Absolute Individual Molecular Weight Distributions from Mixtures of Polymers via Size Exclusion Chromatography−Electrospray Ionization Mass Spectrometry

Two-Point Maximum Entropy Noise Discrimination in Spectra over a Range of Baseline Offsets and Signal-to-Noise Ratios

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