Dead time correction of time distribution measurements

Esposito, Francesco; Spinelli, N.; Velotta, R.; Berardi, V.

doi:10.1063/1.1142219

Cited by 16 publications

(10 citation statements)

References 17 publications

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“…An essentially equivalent result for TOF SIMS data was independently obtained by Stephan et al, who provided correction formulas for both unit‐mass and high‐resolution spectra 10 . Related results have also been obtained by other groups 11,12 …”

Section: Introductionsupporting

confidence: 62%

“…10 Related results have also been obtained by other groups. 11,12 Within the TOF SIMS field, Keenan et al 13 and Tyler and Peterson 14 identified the importance of properly handling saturation effects in multivariate analysis (MVA) of unit-mass imaging data. The approach taken in these studies was to first correct the measured data using the formula given by Stephan et al 10 and then apply techniques such as principal component analysis (PCA) or multivariate curve resolution (MCR).…”

Section: Introductionmentioning

confidence: 99%

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High‐resolution peak analysis in TOF SIMS data

Gelb

Esfahani

Walker

2020

Surface & Interface Analysis

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High mass resolution time‐of‐flight secondary ion mass spectrometry (TOF SIMS) can provide a wealth of chemical information about a sample, but the analysis of such data is complicated by detector dead‐time effects that lead to systematic shifts in peak shapes, positions, and intensities. We introduce a new maximum‐likelihood analysis that incorporates the detector behavior in the likelihood function, such that a parametric spectrum model can be fit directly to as‐measured data. In numerical testing, this approach is shown to be the most precise and lowest‐bias option when compared with both weighted and unweighted least‐squares fitting of data corrected for dead‐time effects. Unweighted least‐squares analysis is the next best, while weighted least‐squares suffers from significant bias when the number of pulses used is small. We also provide best‐case estimates of the achievable precision in fitting TOF SIMS peak positions and intensities and investigate the biases introduced by ignoring background intensity and by fitting to just the intense part of a peak. We apply the maximum‐likelihood method to fit two experimental data sets: a positive‐ion spectrum from a multilayer MoS2 sample and a positive‐ion spectrum from a TiZrNi bulk metallic glass sample. The precision of extracted isotope masses and relative abundances obtained is close to the best‐case predictions from the numerical simulations despite the use of inexact peak shape functions and other approximations. Implications for instrument calibration, incorporation of prior information about the sample, and extension of this approach to the analysis of imaging data are also discussed.

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Section: Introductionsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

High‐resolution peak analysis in TOF SIMS data

Gelb

Esfahani

Walker

2020

Surface & Interface Analysis

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“…Available correction methods seem to be useful for counting rates up to a few ions/pulse (typically 1–5 ions/pulse),12, 13, 21 while, to the best of our knowledge, no reliable and straightforward correction has been reported for higher rates. As suggested by Coates,13 limitations are mainly due to an increase in the apparent noise with the detection rate and the actual upper limit depends on the relationship between the dead time and the pulse time and on the probability distribution function of ion arrivals.…”

Section: Theorymentioning

confidence: 94%

Probing Molecular Wires: Synthesis, Structural, and Electronic Study of Donor–Acceptor Assemblies Exhibiting Long‐Range Electron Transfer

Giacalone¹,

Segura²,

Martín³

et al. 2005

Chemistry A European J

104

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A series of donor-acceptor arrays (C60-oligo-PPV-exTTF; 16-20) incorporating pi-conjugated oligo(phenylenevinylene) wires (oligo-PPV) of different length between pi-extended tetrathiafulvalene (exTTF) as electron donor and C60 as electron acceptor has been prepared by multistep convergent synthetic approaches. The electronic interactions between the three electroactive species present in 16-20 were investigated by UV-visible spectroscopy and cyclic voltammetry (CV). Our studies clearly show that, although the C60 units are connected to the exTTF donors through a pi-conjugated oligo-PPV framework, no significant electronic interactions are observed in the ground state. Interestingly, photoinduced electron-transfer processes over distances of up to 50 Angstroms afford highly stabilized radical ion pairs. The measured lifetimes for the photogenerated charge-separated states are in the range of hundreds of nanoseconds (approximately 500 ns) in benzonitrile, regardless of the oligomer length (i.e., from the monomer to the pentamer). A different lifetime (4.35 micros) is observed for the heptamer-containing array. This difference in lifetime has been accounted for by the loss of planarity of the oPPV moiety that increases with the wire length, as established by semi-empirical (PM3) theoretical calculations carried out with 19 and 20. The charge recombination dynamics reveal a very low attenuation factor (beta = 0.01 +/- 0.005 Angstroms(-1)). This beta value, as well as the strong electron coupling (V approximately 5.5 cm(-1)) between the donor and the acceptor units, clearly reveals a nanowire behavior for the pi-conjugated oligomer, which paves the way for applications in nanotechnology.

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“…For the case of paralyzable dead time, the distortion of the count statistics has been fully discussed in the literature [28][29][30][31][32]. The probability of counting a photon corresponds to the probability that nothing triggered the detector during the time interval t dead , prior to the arrival of the photon in question.…”

Section: Spatially Multiplexed Pnr Detector With a Cw Sourcementioning

confidence: 99%