Measurement of the X-ray mass attenuation coefficients of silver in the 5–20 keV range

Islam, Mohammad Tauhidul; Tantau, Lachlan J.; Rae, Nicholas A.; Barnea, Z.; Tran, Chanh Q.; Chantler, Christopher T.

doi:10.1107/s1600577513024089

Cited by 10 publications

(15 citation statements)

References 39 publications

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“…Figure 2 gives the dark-current corrected attenuations for Fc, in addition to the associated percentage uncertainties for each concentration. 23 The These uncertainties are extremely small, and predictably quite similar for each concentration. They are therefore not significant contributors to the final uncertainty of these measurements.…”

Section: Determining Attenuation Using the Hybridmentioning

confidence: 87%

Accurate X-ray Absorption Spectra of Dilute Systems: Absolute Measurements and Structural Analysis of Ferrocene and Decamethylferrocene

et al. 2016

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X-ray absorption fine structure (XAFS) of ferrocene (Fc) and Decamethylferrocene (DmFc) have been determined on an absolute scale using transmission measurements of multiple solutions of differing concentrations (15 mM, 3 mM, pure solvent) at operating temperatures of 10–20 K. Mass attenuation coefficients and photoelectric absorption cross sections are measured and tabulated for both molecules for an extended energy range in excess of 1.5 keV from the Fe K-shell absorption edge. At these temperatures, the minimization of of dynamic disorder has enabled a critical determination of the oscillatory absorption structures created by multiple-scattering paths of the excited photoelectron. These oscillatory structures are highly sensitive to the local conformation environment of the iron absorber in organometallic structures. Crystallographic and scattering studies have reported both structures characterized by staggered cyclopentadienyl rings, in contrast with low temperature crystallography and recent density functional theoretical predictions. Phase changes in the crystallographic space groups are reported for Fc at different temperatures, raising the possibility of alternative conformation states. Robust experimental techniques are described which have allowed the measurement of XAFS spectra of dilute systems by transmission at accuracies ranging from 0.2% to 2%, and observe statistically significant fine structure at photoelectron wavenumbers extending to >12 Å–1. The subtle signatures of the conformations are then investigated via extensive analysis of the XAFS spectra using the full multiple scattering theory as implemented by the FEFF package. Results indicate a near-eclipsed D 5h geometry for low-temperature Fc, in contrast with a staggered D 5d geometry observed for DmFc. The ability of this experimental approach and data analysis methodology combined with advanced theory to investigate and observe such subtle conformational differences using XAFS is a powerful tool for future challenges and widens the capacity of advanced XAFS to solve a broad range of challenging systems.

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Section: Determining Attenuation Using the Hybridmentioning

confidence: 87%

Accurate X-ray Absorption Spectra of Dilute Systems: Absolute Measurements and Structural Analysis of Ferrocene and Decamethylferrocene

et al. 2016

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“…Data on key experimental systematics including energy calibration, dark current, harmonic contamination and scattering were measured and the spectra corrected using published procedures (Islam et al, 2014;Glover & Chantler, 2009;Tantau et al, 2015;Tran et al, 2004;Barnea et al, 2011). Detailed analytical methodologies are addressed by Chantler et al (2015).…”

Section: Data For This Analysismentioning

confidence: 99%

Structural investigation of mMNi(II) complex isomers using transmission XAFS: the significance of model development

Islam

Chantler

Cheah

et al. 2015

J Synchrotron Radiat

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High-accuracy transmission XAFS determined using the hybrid technique has been used to refine the geometries of bis(N-n-propyl-salicylaldiminato) nickel(II) (n-pr Ni) and bis(N-i-propyl-salicylaldiminato) nickel(II) (i-pr Ni) complexes which have approximately square planar and tetrahedral metal coordination. Multiple-scattering formalisms embedded in FEFF were used for XAFS modelling of the complexes. Here it is shown that an IFEFFIT-like package using weighting from experimental uncertainty converges to a well defined XAFS model. Structural refinement of (i-pr Ni) was found to yield a distorted tetrahedral geometry providing an excellent fit, χr(2) = 2.94. The structure of (n-pr Ni) is best modelled with a distorted square planar geometry, χr(2) = 3.27. This study demonstrates the insight that can be obtained from the propagation of uncertainty in XAFS analysis and the consequent confidence which can be obtained in hypothesis testing and in analysis of alternate structures ab initio. It also demonstrates the limitations of this (or any other) data set by defining the point at which signal becomes embedded in noise or amplified uncertainty, and hence can justify the use of a particular k-range for one data set or a different range for another. It is demonstrated that, with careful attention to data collection, including the correction of systematic errors with statistical analysis of uncertainty (the hybrid method), it is possible to obtain reliable structural information from dilute solutions using transmission XAFS data.

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“…More importantly, the near-edge region shows a generally triangular discrepancy quite separate from the oscillatory solid state effects. This is a general observation for many materials such as silver (Tran et al, 2005;Islam et al, 2014;Tantau et al, 2015), molybdenum (de Jonge et al, 2005;Chantler & Bourke, 2010), tin (de Jonge et al, 2007, copper (Chantler et al, 2001;Glover et al, 2008) and gold Islam et al, 2010). Improvements in theoretical understanding are definitely required in the future especially for the baseline.…”

Section: Quantitymentioning

confidence: 86%

High-accuracy measurement of mass attenuation coefficients and the imaginary component of the atomic form factor of zinc from 8.51 keV to 11.59 keV, and X-ray absorption fine structure with investigation of zinc theory and nanostructure

Ekanayake¹,

Chantler²,

Sier³

et al. 2021

J Synchrotron Radiat

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High-accuracy X-ray mass attenuation coefficients were measured from the first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron. Experimentally measured mass attenuation coefficients deviate by ∼50% from the theoretical values near the zinc absorption edge, suggesting that improvements in theoretical tabulations of mass attenuation coefficients are required to bring them into better agreement with experiment. Using these values the imaginary component of the atomic form factor of zinc was determined for all the measured photon energies. The zinc K-edge jump ratio and jump factor are determined and results raise significant questions regarding the definitions of quantities used and best practice for background subtraction prior to X-ray absorption fine-structure (XAFS) analysis. The XAFS analysis shows excellent agreement between the measured and tabulated values and yields bond lengths and nanostructure of zinc with uncertainties of from 0.1% to 0.3% or 0.003 Å to 0.008 Å. Significant variation from the reported crystal structure was observed, suggesting local dynamic motion of the standard crystal lattice. XAFS is sensitive to dynamic correlated motion and in principle is capable of observing local dynamic motion beyond the reach of conventional crystallography. These results for the zinc absorption coefficient, XAFS and structure are the most accurate structural refinements of zinc at room temperature.

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Measurement of the X-ray mass attenuation coefficients of silver in the 5–20 keV range

Cited by 10 publications

References 39 publications

Accurate X-ray Absorption Spectra of Dilute Systems: Absolute Measurements and Structural Analysis of Ferrocene and Decamethylferrocene

Accurate X-ray Absorption Spectra of Dilute Systems: Absolute Measurements and Structural Analysis of Ferrocene and Decamethylferrocene

Structural investigation of mMNi(II) complex isomers using transmission XAFS: the significance of model development

High-accuracy measurement of mass attenuation coefficients and the imaginary component of the atomic form factor of zinc from 8.51 keV to 11.59 keV, and X-ray absorption fine structure with investigation of zinc theory and nanostructure

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