Line Shape Changes Research Articles

Unveiling Doppler effects and charge phenomena in the elastic scattering of keV electrons on polystyrene

Recoil energy is a phenomenon that is observed in various spectroscopy experiments. Elastic Peak Electron Spectroscopy (also known as Electron Compton Scattering) studies the shape of the elastic peak resulting from electron scattering from solid targets. As the atoms move around their equilibrium position, they scatter the distribution of recoil energies, resulting in a broadening of the elastic peak known as Doppler broadening. Since the hydrogen peak has the largest recoil energy shifts due to the low mass of hydrogen, Elastic Peak Electron Spectroscopy is ideal for the detection of hydrogen. The most important aspects of this method for the detection of hydrogen include electron-induced hydrogen desorption and, in dielectric materials, charge phenomena. This work focuses on the elastic peak spectra of keV electrons impinging on polystyrene, with particular interest in the changes in line shape due to the Doppler effect and surface charge during electron irradiation.

Detecting Chirality-Induced Spin Selectivity in Randomly Oriented Radical Pairs Photogenerated by Hole Transfer.

Chirality-induced spin selectivity (CISS) has the potential to control the spin dynamics of chiral molecules for applications in quantum information science. Here we investigate the effect of CISS on the spin dynamics of radical pair formation following photodriven hole transfer in a pair of donor-chiral bridge-acceptor (D-Bχ-A) enantiomers, where D = 2,2,6,6-tetramethyl[1,3]-dioxolo[4,5-f][1,3]benzodioxole, Bχ = (R)- or (S)-2,2'-dimethoxy-4,4'-diphenyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthalene, and A = naphthalene-(1,4:5,8)-bis(dicarboximide). The results are compared to those obtained on the corresponding achiral D-B-A reference molecule in which B = 2″,3',5',6″-tetramethyl-1,1':4',1″:4″,1‴-quaterphenyl. Photoexcitation of A in a randomly oriented sample of D-Bχ-A in glassy butyronitrile at 85 K results in subnanosecond two-step hole transfer from 1*A to D to form D•+-Bχ-A•-, which was characterized using time-resolved electron paramagnetic resonance (TREPR) spectroscopy at X (9.6 GHz), Q (34 GHz), and W (94 GHz) bands. The spectra show line shape changes that are characteristic of a ∼38% contribution of CISS to the spin dynamics of D•+-Bχ-A•- formation. The line shape changes resulting from CISS are particularly apparent in the TREPR spectra at X-band as predicted by recent theory. These results show that (1) CISS has a significant influence on radical pair dynamics initiated by photodriven hole transfer, which is complementary to our recent electron transfer results, and (2) CISS can be detected using TREPR on radical pairs that are randomly oriented relative to an external magnetic field.

Pressure-induced optical anisotropy of HfS2

The effect of pressure on Raman scattering (RS) in bulk HfS2 is investigated under hydrostatic and non-hydrostatic pressure conditions. The RS line shape does not change significantly in the hydrostatic regime up to P = 9.6 GPa, showing a systematic blueshift of the spectral features. In a non-hydrostatic environment, seven peaks appear in the spectrum at P = 7 GPa, which dominate the RS line shape up to P = 10.5 GPa. The change in the RS line shape manifests a pressure-induced phase transition in HfS2. The simultaneous observation of both low-pressure (LP) and high-pressure (HP) related RS peaks suggests the coexistence of two different phases over a wide pressure range. It is found that the HP-related phase is metastable and persists during the decompression cycle down to P = 1.2 GPa, while the LP-related features eventually recover at even lower pressure. The angle-resolved polarized RS performed under P = 7.4 GPa revealed a strong in-plane anisotropy of both the LP-related A1g mode and the HP peaks. The anisotropy is related to the possible distortion of the structure induced by the non-hydrostatic component of the pressure. The results are explained in terms of a distorted Pnma phase as a possible pressure-induced phase of HfS2.

First-Principles Modeling of the Absorption Spectrum of Crystal Violet in Solution: The Importance of Environmentally Driven Symmetry Breaking.

Theoretical spectroscopy plays a crucial role in understanding the properties of the materials and molecules. One of the most promising methods for computing optical spectra of chromophores embedded in complex environments from the first principles is the cumulant approach, where both (generally anharmonic) vibrational degrees of freedom and environmental interactions are explicitly accounted for. In this work, we verify the capabilities of the cumulant approach in describing the effect of complex environmental interactions on linear absorption spectra by studying Crystal Violet (CV) in different solvents. The experimental absorption spectrum of CV strongly depends on the nature of the solvent, indicating strong coupling to the condensed-phase environment. We demonstrate that these changes in absorption line shape are driven by an increased splitting between absorption bands of two low-lying excited states that is caused by a breaking of the D3 symmetry of the molecule and that in polar solvents, this symmetry breaking is mainly driven by electrostatic interactions with the condensed-phase environment rather than distortion of the structure of the molecule, in contrast with conclusions reached in a number of previous studies. Our results reveal the importance of explicitly including a counterion in the calculations in nonpolar solvents due to electrostatic interactions between CV and the ion. In polar solvents, these interactions are strongly reduced due to solvent screening effects, thus minimizing the symmetry breaking. Computed spectra in methanol are found to be in reasonable agreement with the experiment, demonstrating the strengths of the outlined approach in modeling strong environmental interactions.

In-situ evidence for the existence of surface films in electrochemical machining of copper in nitrate electrolytes

This contribution analyzes the electrochemical etching of copper in a sodium nitrate electrolyte using in-situ Raman spectroscopy. Experiments were conducted in a specially designed process chamber at voltages below, at, and above the limiting current plateau. Below the plateau, a Raman peak at 1050 cm–1 is detected, which is attributed to the symmetrical nitrate ion. However, the line shape changes at and above the plateau. Detailed line shape analysis indicates the presence of a copper nitrate surface film by ex-situ comparison with copper nitrate solutions. In addition, the conductivity and pH of copper nitrate solutions were determined. A 5 M copper nitrate solution exhibits a low conductivity of 55 mS cm–1 and a pH close to 0. A significant influence, especially of the low pH, on the surface structure and therefore on the etching mechanism is assumed.

Tunable zero-field magnetoresistance responses in Si transistors: Origins and applications

The near-zero-field magnetoresistance (NZFMR) response has proven to be a useful tool for studying atomic-scale, paramagnetic defects that are relevant to the reliability of semiconductor devices. The measurement is simple to make and, in some cases, simple to interpret. In other cases, more sophisticated modeling based on the stochastic Liouville equation (SLE) is needed to access valuable information from NZFMR results. It has been shown that hyperfine and dipolar coupling interactions at atomic-scale defects affect the NZFMR line shape, but experimental parameters related to the detection method of NZFMR can also affect the nature of the response. Here, we demonstrate four distinct NZFMR detection methods in Si MOSFETs, which all access identical Si/SiO2 interface defects. In all four cases, we show that the line shape of the response is tunable based on experimental parameters alone. Using SLE-based modeling, we verify that time constants connected to physical carrier capture rates at the defect sites lead to these NZFMR line shape changes. The results demonstrate a method to extract some atomic-scale information for the purpose of defect identification. They also have broader applications to the continued development of ultra-sensitive magnetometers based on NZFMR in semiconductors. Additionally, the NZFMR effect in common Si-based devices may provide an inexpensive and accessible platform that mimics similar radical pair mechanisms that have become increasingly important in various biology fields.

Blue-Emitting Cs(Pb,Cd)Br3 Nanocrystals Resistant to Electric Field-Induced Ion Segregation.

High-performance solution-processed perovskite light-emitting diodes (PeLEDs) have emerged as a good alternative to the well-established technology of epitaxially grown AIIIBV semiconductor alloys. Colloidal cesium lead halide perovskite nanocrystals (CsPbX3 NCs) exhibit room-temperature excitonic emission that can be spectrally tuned across the entire visible range by varying the content of different halogens at the X-site. Therefore, they present a promising platform for full color display manufacturing. Engineering of highly efficient PeLEDs based on bromide and iodide perovskite NCs emitting green and red light, respectively, does not face major challenges except low operational stability of the devices. Meanwhile, mixed-halide counterparts demonstrating blue luminescence suffer from the electric field-induced phase separation (ion segregation) phenomenon described by the rearrangement (demixing) of mobile halide ions in the crystal lattice. This phenomenon results in an undesirable temporal redshift of the electroluminescence spectrum. However, to realize spectral tuning and, at the same time, address the issue of ion segregation less mobile Cd2+ ion could be introduced in the lattice at Pb2+-site that leads to the band gap opening. Herein, we report an original synthesis of CsPb0.88Cd0.12Br3 perovskite NCs and study their structural and optical properties, in particular electroluminescence. Multilayer PeLEDs based on the obtained NCs exhibit single-peak emission centered at 485 nm along with no noticeable change in the spectral line shape for 30 min which is a significant improvement of the device performance.

Construction Monitoring and Results Analysis of a Certain Major Bridge

The construction method of continuous beam bridges is mostly cantilever casting in place, which has a long construction period and complex process, and is influenced by various factors. Therefore, it can have many adverse effects on the internal forces and deformation of the main beam. To ensure that the line shape of the main beam meets the design and regulatory requirements and that the internal forces of the completed bridge are close to the theoretical design values, ensuring the safe construction of the bridge, it is necessary to monitor the entire construction process of the bridge. This paper takes a certain major bridge as the background, monitors the entire construction process of the main bridge, collects the deflection values at control points and stress values at control interfaces at each construction stage, and compares the measured values with theoretical results. This allows for a comprehensive understanding of the line shape changes and safety conditions of the bridge, assures the reliability and safety of the structure during construction, ensures that the relative elevation deviation of the closure section is less than the permitted values by standards, and makes sure that the line shape of the main beam after completion meets the design specifications.

Characterization of K2-167 b and CALM, a new stellar activity mitigation method

ABSTRACT We report precise radial velocity (RV) observations of HD 212657 (= K2-167), a star shown by K2 to host a transiting sub-Neptune-sized planet in a 10 d orbit. Using Transiting Exoplanet Survey Satellite (TESS) photometry, we refined the planet parameters, especially the orbital period. We collected 74 precise RVs with the HARPS-N spectrograph between August 2015 and October 2016. Although this planet was first found to transit in 2015 and validated in 2018, excess RV scatter originally limited mass measurements. Here, we measure a mass by taking advantage of reductions in scatter from updates to the HARPS-N Data Reduction System (2.3.5) and our new activity mitigation method called CCF Activity Linear Model (CALM), which uses activity-induced line shape changes in the spectra without requiring timing information. Using the CALM framework, we performed a joint fit with RVs and transits using exofastv2 and find Mp = $6.3_{-1.4}^{+1.4}$ $\, M_{\hbox{$\oplus $}}$ and Rp = $2.33^{+0.17}_{-0.15}$ $\, R_{\hbox{$\oplus $}}$, which places K2-167 b at the upper edge of the radius valley. We also find hints of a secondary companion at a ∼22 d period, but confirmation requires additional RVs. Although characterizing lower mass planets like K2-167 b is often impeded by stellar variability, these systems especially help probe the formation physics (i.e. photoevaporation, core-powered mass-loss) of the radius valley. In the future, CALM or similar techniques could be widely applied to FGK-type stars, help characterize a population of exoplanets surrounding the radius valley, and further our understanding of their formation.

Precise Radial Velocities Using Line Bisectors

We study the properties of line bisectors in the spectrum of the Sun-as-a-star, as observed using the Integrated Sunlight Spectrometer (ISS) of the SOLIS project. Our motivation is to determine whether changes in line shape due to magnetic modulation of photospheric convection can be separated from the 9 cm s−1 Doppler reflex of the Earth’s orbit. Measuring bisectors of 21 lines over a full solar cycle, our results overwhelmingly indicate that solar magnetic activity modulates photospheric convection so as to reduce the asymmetries of line profiles in the spectrum of the Sun-as-a-star (having both C-shaped and reversed-C-shaped bisectors). However, some lines are constant or have variations in shape that are too small to measure. We inject a 9 cm s−1 radial velocity signal with a 1 yr period into the ISS spectra. Informed by a principal component analysis of the bisectors, we fit the most significant components to the bisectors of each line by linear regression, including a zero-point offset in velocity that is intended to capture the injected radial velocity signal. Averaging over lines, we are able to recover that signal to solid statistical significance in the presence of much larger changes in the line shapes. Although our work has limitations (that we discuss), we establish that changes in absorption line shapes do not in themselves prevent the detection of an Earth-like planet orbiting a Sun-like star using precise radial velocity techniques.

Drop That Activation Energy: Tetragonal to Cubic Transformations in Na3PS4−xSex for Solid State Sodium Ion Battery Materials

AbstractSodium‐containing chalcogenide materials are emerging as a class of solid electrolytes for application in inexpensive all‐solid‐state sodium‐ion batteries due to their high ionic conductivity, abundance, and degree of synthetic and structural variability. Members of the solid solution Na3PS4−xSex, which are promising solid electrolytes for sodium‐ion batteries, are prepared by reaction at high temperature. With increasing substitution of S by Se, the structure transforms from tetragonal (space group P21c for x = 0, 1) to cubic (space group I3m for x = 2, 3, 4). Within the solid solution, the S and Se atoms are completely disordered in the environments around the P atoms, in accordance with a binomial distribution, as inferred by the 31P nuclear magnetic resonance (NMR) spectra. In 23Na NMR experiments conducted at different magnetic fields and temperatures, quadrupolar lineshapes are observed that are influenced by sodium ion dynamics; the activation energies decrease from 0.21 to 0.15 eV on progressing from the S‐ to the Se‐rich members. A dynamic model is proposed to account for the changes in the 23Na quadrupolar lineshapes by switching the orientations of the electric field gradient and chemical shift anisotropy tensors when Na+ ions hop to the four nearest Na sites.

Subsurface nitrogen bonding and thermal stability of low-energy nitrogen implanted H-Diamond (100) surfaces studied by XPS and HREELS

We investigate the surface/subsurface bonding, retention, and thermal stability of nitrogen in H-Diamond (100) implanted with 200 eV N2+ at a dose of 1×1014 ions/cm2 (D1) in comparison to a dose of 3-4×1014 ions/cm2 (D2) and to nitrogen adsorbed on the surface (by MW(N2) exposure) by electron spectroscopy. For D1, the N(1s) XP line displays a single symmetric peak associated with C‒N/C=N species, concurrently observing a minor C=C/C(def) component in C(1s). The N(1s) line intensity decreases linearly with annealing temperature without changes in line shape. This could be due to competition of diffusion of trapped nitrogen from interstitial positions followed by desorption and recombination of the implanted nitrogen with carbon vacancies, resulting in very thermally stable nitrogen species. The latter process is dominant at ∼700 °C where the onset of vacancies diffusion in diamond occurs. For D2, an additional component associated with CN(nitrile-like) bonds is observed. From vibrational spectroscopy, the H-Diamond surface implanted with a D1 dose displays features associated with nitrogen bonding to carbon atoms and hydrogen bonding to the diamond surface and defects. Unlike the MW(N2) plasma case, no NHx(ads) bonds are identified upon implantation. High-temperature annealing shows that for the D1 dose, partial surface structural recovery occurs.

Lipid- and substrate-induced conformational and dynamic changes in a glycosyltransferase involved in E. coli LPS synthesis revealed by 19F and 31P NMR

WaaG is a glycosyltransferase (GT) involved in the synthesis of the bacterial cell wall, and in Escherichia coli it catalyzes the transfer of a glucose moiety from the donor substrate UDP-glucose onto the nascent lipopolysaccharide (LPS) molecule which when completed constitutes the major component of the bacterium's outermost defenses. Similar to other GTs of the GT-B fold, having two Rossman-like domains connected by a short linker, WaaG is believed to undergo complex inter-domain motions as part of its function to accommodate the nascent LPS and UDP-glucose in the catalytic site located in the cleft between the two domains. As the nascent LPS is bulky and membrane-bound, WaaG is a peripheral membrane protein, adding to the complexity of studying the enzyme in a biologically relevant environment. Using specific 5-fluoro-Trp labelling of native and inserted tryptophans and 19F NMR we herein studied the dynamic interactions of WaaG with lipids using bicelles, and with the donor substrate. Line-shape changes when bicelles are added to WaaG show that the dynamic behavior is altered when binding to the model membrane, while a chemical shift change indicates an altered environment around a tryptophan located in the C-terminal domain of WaaG upon interaction with UDP-glucose or UDP. A lipid-bound paramagnetic probe was used to confirm that the membrane interaction is mediated by a loop region located in the N-terminal domain. Furthermore, the hydrolysis of the donor substrate by WaaG was quantified by 31P NMR.

Polarization control investigation based on an integrated graphene-assisted microring cavity

In this paper, we propose and analyze an integrated polarization-selective structure of a graphene-assisted silica microring cavity to realize polarization control due to different optical distributions of whispering-gallery modes in the microring and polarization-dependent absorptions of graphene. A graphene stripe is partially side coupled with a silica microring to distinctly influence the propagations of a TE mode and TM mode in the microring. Especially, the appearance of the plasmonic mode in the groove between the graphene and the microring enhances light–matter interaction between the graphene and the TM-polarized mode, while without that for the case of TE mode propagation. By applying voltage on the graphene stripe along with its electro-optic modulation effect, the difference in the polarization extinction ratio of 20.6 dB is obtained between the cases of the polarized TM mode and TE mode in the microring. Furthermore, a second silica microring is added in this hybrid structure to couple the original microring along with a graphene stripe embedded in between finally realizing an electromagnetically induced transparency line shape because of the plasmonic coupling in both cavities with the condition of TM mode propagation, while without any line-shape change for the case of TE mode propagation. This compact hybrid structure offers a good integrated photonic platform to realize an excellent polarization-selective device.

Why matrix-decomposition of overlapped light spectroscopic features leads to overfitting in certain cases ?

Overfitting refers to spurious correlations that inflate prediction outcomes and result in misleadingly optimistic models. We investigate the case of systematic overfitting occurring when changes in bandwidths, positions and line shapes are introduced to spectra with strongly overlapped bands and are modeled using popular matrix-decomposition techniques because these parameters amplify variance in steep spectral sections in a manner detached from any chemical or physical interpretations. Our analysis of the geometry of profile shapes demonstrates how indirect assessment of lateral spectral changes distorts original spectral information and creates unnecessary complexity that results in misleading interpretations. Alternative strategy is proposed that remedies this situation and aims to generally improve stability of spectral modeling in the future.

Running safety assessment of trains considering post-earthquake damage state of bridge–track system

A bridge–track system (BTS) is inevitably damaged during an earthquake; this is reflected in its stiffness deterioration and residual deformation, which affect the post-earthquake running safety of trains. The influence of the post-earthquake damage state of an actual BTS on train running safety remains unclear. Hence, this study mainly discussed the influence of post-earthquake bridge–track damage state and residual deformation on running safety and established a safe speed limit for trains under different seismic intensities. A finite element (FE) model of a simply supported railway BTS was established using the OpenSees software. A nonlinear seismic response analysis was performed under different ground motion intensities (0.1, 0.3, and 0.6 g for frequent, design, and rare earthquakes, respectively), and bridge damage, fastener damage, and residual deformation of the rail after the earthquakes were studied. An OpenSees-TRBF (train-rail-bridge-foundation coupled system dynamic analysis software, TRBF) co-simulation method was developed to analyze the running safety of trains after earthquakes under a damaged state of the BTS based on the TCP/IP communication interaction technology. A safe speed limit for trains considering the post-earthquake damage state and residual deformation was proposed, providing a reference for the post-earthquake capacity of trains. The results of the BTS seismic damage analysis showed that the residual displacement of the bearing was the fundamental reason for the change in the rail line shape, and fastener damage mainly occurred in the range of 2–4 fasteners at the end of the girder under the design and rare earthquakes. The results of the running safety analysis showed that, if damage to the BTS is ignored, the running safety after an earthquake will be misjudged. Based on the continuous overrun time limit index, the running safety indices for ground motion intensities of 0–0.4, 0.4–0.5, and 0.5–0.6 g could meet the speed requirements of 350, 300, and 150 km/h, respectively. This study provides some references and suggestions for the running safety of trains following an earthquake.

Characterization of Effects of Compressed Sensing on High Spectral and Spatial Resolution (HiSS) MRI with Comparison to SENSE.

High Spectral and Spatial resolution (HiSS) MRI shows high diagnostic performance in the breast. Acceleration methods based on k-space undersampling could allow stronger T2*-based image contrast and/or higher spectral resolution, potentially increasing diagnostic performance. An agar/oil phantom was prepared with water-fat boundaries perpendicular to the readout and phase encoding directions in a breast coil. HiSS MRI was acquired at 3T, at sensitivity encoding (SENSE) acceleration factors R of up to 10, and the R = 1 dataset was used to simulate corresponding compressed sensing (CS) accelerations. Image quality was evaluated by quantifying noise and artifact levels. Effective spatial resolution was determined via modulation transfer function analysis. Dispersion vs. absorption (DISPA) analysis and full width at half maximum (FWHM) quantified spectral lineshape changes. Noise levels remained constant with R for CS but amplified with SENSE. SENSE preserved the spatial resolution of HiSS MRI, while CS reduced it in the phase encoding direction. SENSE showed no effect on FWHM or DISPA markers, while CS increased FWHM. Thus, CS might perform better in noise-limited or geometrically constrained applications, but in geometric configurations specific to breast MRI, spectral analysis might be compromised, decreasing the diagnostic performance of HiSS MRI.

Temperature and anion ligand field dependence of LnCl3 (Ln = Nd, Dy, Sm) electronic absorption spectra in LiCl–KCl eutectic molten salt

A comprehensive knowledge of the coordination, bonding, and speciation of elements in molten salt mixtures is necessary to understand and predict the chemical and physical properties of the salt. Absorption spectroscopy can yield information about the chemistry of species of interest in alkali halide molten salt mixtures by revealing information about the electronic structure and transitions of those species. In this study, ultraviolet (UV), visible (vis), and near-infrared (NIR) absorption spectroscopy was used to examine changes to the electronic structure of trivalent Nd, Sm, and Dy in LiCl–KCl eutectic molten salt with changes in temperature and the anion composition of the melt. With increasing temperature, changes to spectral features suggest a distortion of the coordination complexes. Changes to lineshape with the substitution of alternative halide anions were examined and analyzed, revealing differences in the coordination for I− versus F− with the lanthanides. Gaussian peak fitting was used to show that the changes in lineshape with the progressive addition of F− anions can be explained by the superposition of a set of absorption bands from complexes with all Cl− anion ligands and a set of blueshifted absorption bands from complexes containing both F− and Cl− anion ligands. This work yields a new method to analyze and interpret change to electronic absorption spectra for f-block elements dissolved in alkali halide molten salts as well as new observations of the interactions of larger and smaller halide anions with lanthanides in Cl−-based molten salts.

Fluorescence in colloidal solutions: Scattering vs physicochemical effects on line shape

Line shapes of anionic fluorescein fluorescence in suspensions of polystyrene nanoparticles (PSNP), anionic and cationic micelles, lipid vesicles, and of laurdan in lipid vesicles were investigated. Computed second harmonic of measured spectra indicated three lines for fluorescein and two for laurdan. Accordingly, fluorescein spectra were fit to three Gaussians and laurdan spectra to two lognormal distributions. Resolved line parameters were examined against particle concentration. Scattering, although wavelength dependent, affected intensity but not line shape. Inner filter effects of scattering on line shape are insignificant because multiple scattering, redirection of scattered photons into the detector, and inclusion of scattered photons in collection and detection minimize wavelength dependent effects. Dominant effects on line width and peak positions are due to physicochemical effects of dye-particle-solvent interactions rather than scattering. Fluorescein does not interact with anionic micelles and lipid vesicles, but remains in the aqueous phase, and responds to pH increase induced by these additives. Blue shift in peak position, decrease in line width, and increase in emission intensity in these systems are like those in NaOH solutions. Fluorescein does interact with cationic micelles and hydrophobic PSNP, and its emission is red shifted. Laurdan in lipid vesicles senses interface polarity. Blue shift and decrease in line width of its emission line indicate decreasing polarity with lipid concentration. Scattering, as well as interactions affect emission intensity. Physicochemical effects distort line shape and modify intrinsic spectra. Line shape changes are better markers than intensity to investigate interactions and reactions.

Resonant double-core excitations with ultrafast, intense X-ray pulses

Intense few-to-sub-femtosecond soft X-ray pulses can produce neutral, two-site excited double-core-hole states by promoting two core electrons to the same unoccupied molecular orbital. We theoretically investigate double nitrogen K-edge excitations of nitrous oxide (N 2 O) with multiconfigurational electronic structure calculations. We show that the second core-excitation energy is reduced with respect to its ground state value. A site-selective double core-excitation mechanism using intense few-femtosecond x-rays is investigated using time-dependent Schrödinger equation (TDSE) simulations. The subsequent two-step Auger–Meitner and two-electrons-one-electron decay spectra of the double core-excited states are analysed using a Mulliken population analysis of the multiconfirational wavefunctions. The change in the electron emission lineshape between the absorption of 1 or 2 photons in the resonant core-excitation is predicted by combining this approach with the TDSE simulations. We examine the possibility of resolving the double core-excited states with X-ray pump-probe techniques by calculating the chemical shifts of the core-electron binding energy of the core-excited states and decay products.