Dirac–Fock photoionization parameters for HAXPES applications

Trzhaskovskaya, M. B.; Yarzhemsky, V. G.

doi:10.1016/j.adt.2017.04.003

Cited by 95 publications

(56 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have assumed that the “ f ” ratio is unity. The error from this assumption is difficult to evaluate, but through an analysis using TY quadrupole terms, the expected X‐ray polarisation because of Bragg reflection and corrections for single scattering albedos for these elements, we find that it could contribute approximately 5% error, but have not made these corrections as they do not change the scatter, nor the mean value, we find in the result.…”

Section: Reference Spectra For Ag Lαmentioning

confidence: 99%

“…To calculate our approximate AMRSFs, we used Dirac‐Hartree‐Fock‐Slater cross sections from Sabbatucci and Salvat (SS), which agree closely with Scofield's cross sections but have the advantage of being accessible as a digital database and covering a finer energy mesh. We also tabulated the Dirac‐Fock cross sections, dipole, and non‐dipole angular emission parameters of Trzhaskovskaya and Yarzhemsky (TY) . These only contain photoelectron lines accessible to Al Kα radiation, but are useful for assessing the uncertainties of some of the values used.…”

Section: Average Matrix Relative Sensitivity Factors (Amrsfs)mentioning

confidence: 99%

See 1 more Smart Citation

Intensity calibration and sensitivity factors for XPS instruments with monochromatic Ag Lα and Al Kα sources

Shard

Counsell²,

Cant

et al. 2019

Surface & Interface Analysis

View full text Add to dashboard Cite

This paper provides a description of the transmission function of an X‐ray photoelectron spectroscopy (XPS) instrument operating with exchangeable Al Kα (1486.6 eV) and Ag Lα (2984.3 eV) sources. Both sources use the same quartz crystal monochromator and illuminate the same area of the sample. The transmission‐function–corrected data from sputter cleaned gold provides a useful reference material to calibrate other instruments of the same type. Sensitivity factors for Ag Lα and Al Kα are calculated from photoionisation cross sections and electron effective attenuation lengths. These compare well with previous experimental values and data acquired from ionic liquids. The intensity of the Ag Lα source is found to be approximately 50 times lower than the Al Kα source. This, coupled with generally lower photoemission efficiencies, results in noisier data or extended acquisition times. However, there are clear advantages to using the Ag Lα source to analyse certain elements where additional core levels can be accessed and for many technologically important elements where interference from Auger electron peaks can be eliminated. The combination of calibrated data from both sources provides direct and easily interpreted insight into the depth distribution of chemical species. This could be particularly important for topographic samples, where angle resolved experiments are not always helpful. We also demonstrate, using thin coatings of chromium and carbon, that the inelastic background in Ag Lα wide‐scan spectra has a significantly increased information depth compared with Al Kα.

show abstract

Section: Reference Spectra For Ag Lαmentioning

confidence: 99%

Section: Average Matrix Relative Sensitivity Factors (Amrsfs)mentioning

confidence: 99%

Intensity calibration and sensitivity factors for XPS instruments with monochromatic Ag Lα and Al Kα sources

Shard

Counsell²,

Cant

et al. 2019

Surface & Interface Analysis

View full text Add to dashboard Cite

show abstract

“…The earlier models of electronic structures of actinide (Np, Pu, Am) dioxides in references [7][8][9] employed density of states (DOS) calculations for several lattice fragments including the 279-atom An 63 O 216 cluster. The comparisons of the results for the smallest and largest fragments (AnO 8 and An 63 O 216 ) showed that in all cases the increase in the cluster size leads to the transformation of discrete levels into the band structure, while the positions of the orbital groups and the corresponding bands remain close to each other. Furthermore, the effects of the An 6s, 6p, 5f, 6d, 7s, 7p overlapping with the O 2s, 2p orbitals (ie, the MO structure) for various fragments were also close to each other.…”

Section: Resultsmentioning

confidence: 96%

“…the U 13 O 56 and U 63 O 216 clusters, reflecting the bulk of solid uranium dioxide. The bar graph of the theoretical valence band (from 0 to~35 eV) of XPS spectrum was built such that it was in satisfactory agreement with the experimental spectrum of a UO 2 single crystalline thin film.…”

mentioning

confidence: 99%

The nature of the chemical bond in UO₂

Maslakov

Teterin

Ryzhkov

et al. 2019

Int J of Quantum Chemistry

View full text Add to dashboard Cite

The nature of the chemical bond in UO2 was analyzed taking into account the X‐ray photoelectron spectroscopy (XPS) structure parameters of the valence and core electrons, as well as the relativistic discrete variation electronic structure calculation results for this oxide. The ionic/covalent nature of the chemical bond was determined for the UO8 (D4h) cluster, reflecting uranium's close environment in UO2, and the U13O56 and U63O216 clusters, reflecting the bulk of solid uranium dioxide. The bar graph of the theoretical valence band (from 0 to ~35 eV) of XPS spectrum was built such that it was in satisfactory agreement with the experimental spectrum of a UO2 single crystalline thin film. It was shown that unlike the crystal field theory results, the covalence effects in UO2 are significant due to the strong overlap of the U 6p and U 5f atomic orbitals with the ligand orbitals, in addition to the U 6d atomic orbital (AO). A quantitative molecular orbital (MO) scheme for UO2 was built. The contribution of the MO electrons to the chemical bond covalence component was evaluated on the basis of the bond population values. It was found that the electrons of inner valence molecular orbitals (IVMO) weaken the chemical bond formed by the electrons of outer valence molecular orbitals (OVMO) by 32% in UO8 and by 25% in U63O216.

show abstract

“…The effective volume contributing to the diffraction signal is limited by inelastic scattering. At E final = 7015 eV (panel (j)) the inelastic mean free path in graphite is λ IMFP ≈20 nm . The amplitude of an electron wave traveling in a certain direction in k ‐space drops to 10% of its initial value within a distance of 2.4 λ IMFP ≈48 nm.…”

Section: Photoelectron Momentum Microscopymentioning

confidence: 99%

Electron‐ and X‐Ray Spectroscopies of Organic Charge‐Transfer Complexes

Medjanik

Elmers

Schönhense

et al. 2019

Physica Status Solidi (b)

View full text Add to dashboard Cite

Recent work aiming at a deeper understanding of the electronic properties of classical and novel charge‐transfer (CT) complexes is reviewed herein. From a variety of studied CT salts, the prototypical examples TTF‐TCNQ, (TMTTF)2SbF6, (TMTSF)2PF6, and TMP/HMP‐TCNQ have been selected. Three different types of electron and X‐ray spectroscopies were applied, namely ultraviolet photoelectron spectroscopy (UPS), hard X‐ray photoelectron spectroscopy (HAXPES), and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy. Using UPS, the development of the valence band structure during co‐deposition of the donor and acceptor moieties TMP/HMP and TCNQ has been studied. The spectra reveal characteristic level shifts and a strong reduction of the HOMO–LUMO gap upon formation of the complex. HAXPES probes the core levels and reveals characteristic shifts of the binding energies in (TMTTF)2SbF6 at the phase transition to the low‐temperature charge‐ordered state. NEXAFS is a local, element‐specific probe for the unoccupied bands above the Fermi level and reveals changes in the population of specific orbitals when the CT complex is formed. As an outlook, the novel method of photoelectron momentum microscopy is presented, giving access to the valence bands and core‐levels and in particular to high‐resolution X‐ray photoelectron diffraction patterns.

show abstract

Dirac–Fock photoionization parameters for HAXPES applications

Cited by 95 publications

References 29 publications

Intensity calibration and sensitivity factors for XPS instruments with monochromatic Ag Lα and Al Kα sources

Intensity calibration and sensitivity factors for XPS instruments with monochromatic Ag Lα and Al Kα sources

The nature of the chemical bond in UO₂

Electron‐ and X‐Ray Spectroscopies of Organic Charge‐Transfer Complexes

Contact Info

Product

Resources

About