Redistribution Of Density Research Articles

TD-DFT study of BIPS spiropyran: Effects of functionals and high-polarity solvent on Cspiro O bond dissociation and recovery.

We performed a theoretical analysis of the BIPS photochemical cycle using an extensive set of forty hybrid functionals and taking into account a highly polar solvent (methanol). The functionals with a small fraction of the exact Hartree-Fock exchange (%HF) showed the predominant S0 → S2 transition with the strengthening of the Cspiro O bond. At the same time, functionals with medium and high %HF (including those with long-range correction) gave a dominant S0 → S1 transition with weakening or breaking of the Cspiro O bond, which corresponds to the experimental results. The influence of a highly polar solvent on the photochemical electrocyclic transformations of BIPS turned out to be significant. The number of functionals causing dissociation of the Cspiro O bond decreased from 10 to 7 compared to the gas phase. The magnitude of the oscillator strength has increased by approximately one and a half times. Structural distortions of the BIPS molecule during excitation (both with and without Cspiro O bond cleavage) significantly decreased in methanol compared to the gas phase. The two strong hydrogen bonds of methanol molecules with the oxygen and nitrogen atoms of spiropyran also have a significant effect on its excitation. They lead to a change in the predominant transition from S0 → S2 to S0 → S1 for five functionals. The number of functionals giving dissociation of the Cspiro O bond decreased from seven to four (M08HX, M052X, CAM-B3LYP, and M11). After the opening of the excited BIPS molecule, both of its strong H-bonds with methanol are preserved. Of this set of four functionals, only M052X and CAM-B3LYP exhibited the dominant HOMO-1 → LUMO configuration observed in high-level computations by other authors. Therefore, both of these functionals are recommended for modeling the photochemical cycle of this spiropyran. The photochemical cycle of BIPS was theoretically analyzed. The redistribution of the electron density in this cycle was quantitatively described using the differences in NPA of the atomic charges. The most important result of this analysis was the electrostatic mechanism of the approach of Cspiro and oxygen atoms at the fourth stage, which causes further reduction of the Cspiro O bond.

Metal-support interaction promoted multifunctional electrocatalysis on PtCo/NC with ultralow Pt loading for oxygen reduction reaction and zinc-air battery

Tri-functional PtCo/NC nanocatalysts were assembled via in-situ integration with ultralow Pt loading supported on ZIF-67 derived porous carbon material, and used as electrocatalysts for oxygen reduction reaction (ORR), ethanol oxidation reaction (EOR), hydrogen evolution reaction (HER). Detailedly, PtCo-3/NC with ultralow Pt loading (1 wt%) exhibits the halfwave potential of 0.877 V for ORR in acidic media and considerable current density for both ORR and EOR at 0.85 V, and low overpotential (η10 =10 mV) for HER. The as-assembled zinc-air batteries (ZABs) based on PtCo/NC have higher power density than Pt/C based ZABs. DFT calculation reveals the strong metal-support interactions (MSI) in PtCo/NC, which leads to the change of electronic state, redistribution of charge density and optimization of free energy, allowing it to present greater performances than Pt/C. This work highlights the possibility of using it as highly effective electrode catalysts with ultralow Pt loading in fuel cells and metal-air battery.

The Electric Field Evaluation for Vibrating Rain Droplets on the Overhead Line Conductors

The water droplets on the surface of the overhead line (OHL) conductors are subject to an intensive electric field, which induces electric force on the charged liquid surface. Under the combined action of the surface tension as well as the electric force, movement and deformation can be observed on those water droplets. These result in a re-distribution of charge density on the liquid surface and therefore a re-distribution of electric force. In this paper, in order to strengthen the understanding of this complex multi-physics problem of interaction and mutual coupling, the vibration characteristics of water droplets under alternating electric fields is studied using the finite element method (FEM). Parameters such as the volume size of the water droplet, static/dynamic contact angle between the water droplet and conductor surface and voltage level are studied in relation to the vibration characteristics. The reproducible correlation between the phase and amplitude of the water droplet vibration on the surface of the conductor and the applied voltage is established. According to the calculated instantaneous electric field strength, it is explained that protrusions such as water droplets are the starting point of corona discharge.

A Comparative XPS, UV PES, NEXAFS, and DFT Study of the Electronic Structure of the Salen Ligand in the H2(Salen) Molecule and the [Ni(Salen)] Complex.

A comparative study of the electronic structure of the salen ligand in the H2(Salen) molecule and the [Ni(Salen)] complex was performed using the experimental methods of XPS, UV PES, and NEXAFS spectroscopy along with DFT calculations. Significant chemical shifts of +1.0 eV (carbon), +1.9 eV (nitrogen), and -0.4 eV (oxygen) were observed in the 1s PE spectra of the salen ligand atoms when passing from a molecule to a complex, unambiguously indicating a substantial redistribution of the valence electron density between these atoms. It is proposed that the electron density transfer to the O atoms in [Ni(Salen)] occurred not only from the Ni atom, but also from the N and C atoms. This process seemed to be realized through the delocalized conjugated π-system of the phenol C 2p electronic states of the ligand molecule. The DFT calculations (total and partial DOS) for the valence band H2(Salen) and [Ni(Salen)] described well the spectral shape of the UV PE spectra of both compounds and confirmed their experimental identification. An analysis of the N and O 1s NEXAFS spectra clearly indicated that the atomic structure of the ethylenediamine and phenol fragments was retained upon passing from the free salen ligand to the nickel complex.

In-Plane Hydrogen Bonds and Out-of-Plane Dipolar Interactions in Self-Assembled Melem Networks

Melem (2,6,10-triamino-s-heptazine) is the building block of melon, a carbon nitride (CN) polymer that is proven to produce H2 from water under visible illumination. With the aim of bringing additional insight into the electronic structure of CN materials, we performed a spectroscopic characterization of gas-phase melem and of a melem-based self-assembled 2D H-bonded layer on Au(111) by means of ultraviolet and X-ray photoemission spectroscopy (UPS, XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In parallel, we performed density functional theory (DFT) simulations of the same systems to unravel the molecular charge density redistribution caused by the in-plane H-bonds. Comparing the experimental results with the spectroscopic DFT simulations, we can correlate the induced charge accumulation on the Namino atoms to the red-shift of the corresponding N 1s binding energy (BE) and of the Namino 1s → LUMO+n transitions. Moreover, when introducing a supporting Au(111) surface in the computational simulations, we observe a molecule–substrate interaction that almost exclusively involves the out-of-plane molecular orbitals, leaving those engaged in the in-plane H-bonded network rather unperturbed.

Study on ESIPT of salicylaldehyde derivative EQCN in DCM solvent

The fluorescence of salicylaldehyde derivative (EQCN) as an excitation-wavelength-dependent molecule with long-persistent luminescence has been investigated experimentally and theoretically. However, the excited-state intramolecular proton transfer (ESIPT) process mechanism and optical property associated with photochemical process of EQCN molecule in dichloromethane (DCM) solvent has not been discussed in detail. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to investigate ESIPT process of EQCN molecule in DCM solvent. By optimizing the geometry of the EQCN molecule, the hydrogen bond interaction of EQCN molecule of Enol structure in excited state (S1 state) is strengthened. The calculated absorption peak and fluorescence peak agree well with the experimental values. Based on the optimized geometric structure, the frontier molecular orbital isosurface (FMOs) were drawn, and the redistribution of electron density in DCM solvent was depicted, which intuitively explain the changes in the photophysical properties of EQCN. Through the calculated potential energy curves (PECs) of EQCN in both DCM solvent and ethanol solvent, the ESIPT process of EQCN was found more likely to occur in ethanol solvents.

Dispersion interactions with analytes at the center of graphene nanoflakes turn into electrostatic at the edge

Adsorption of small gaseous molecules on the center and edges of polycyclic aromatic hydrocarbons is studied through density functional theory calculations. The choice of selected functional for the study is based on a benchmarking, where 37 functionals are evaluated at low cost basis set against high level DFT SAPT calculations for adsorption of water molecule on coronene and hexabenzocoronene. After benchmarking, the detailed analysis is performed for the adsorption of H2S, H2O, NH3, CH3OH, HCN, H2O2 and NH2NH2 on coronene at its center and edges. The coronene is chosen to better elucidate the edge effect on the adsorption of analytes. All of the studied analytes are physiosorbed on coronene with adsorption energies ranging from 1 to 6 kcal mol−1. These complexes are stabilized by X-H---π interactions between analytes and coronene surface. The SAPT0 analysis reveals that the X-H---π interactions at the center (non-edge) position of coronene are dominated by dispersion interaction whereas the similar interactions at the edges are dominated by electrostatic interactions. The change from dispersion to electrostatic on edges is attributed to polarization of the systems by C–H polarity differences. The complexes having lone pair---π interactions have unexpectedly repulsive electrostatic interactions in H2S@GNF and NH3@GNF complexes. Electronic properties reveal that coronene surface is highly selective for hydrazine whereas adsorption of other analytes does not bring any significant changes in the electronic structure of coronene. The high selectivity of coronene for NH2NH2 is also evident from the redistribution of densities in frontier molecular orbitals. For NH2NH2@GNF complexes, the HOMOs are present on hydrazine whereas LUMOs are present in coronene. For other analytes, HOMOs and LUMOs are present merely on graphene nanoflake. This high sensitivity of coronene for hydrazine is due to better overlap of frontier molecular orbitals of analyte with coronene.

Synthesis and spectral properties of new xanthene-like fluorophore and light-filter

By the reaction of N'-(4-formyl-2,3-dihydro-1H-benzo[b]xanthen-12-yl)-N,N-dimethylimidoformamide and N'-(6-formyl-7,8,9,10- tetrahydrocyclohepta[b]chromen-11-yl)-N,N-dimethylimidoformamide with malononitrile and cyanoacetic acid ethyl ester, the following two new dyes were synthesized by basic catalysis: N'-[4-(2,2-dicyanovinyl)-2,3-dihydro-1H-benzo[b]xanthen-12-yl]-N,N-dimethylimidoformamide and ethyl (2E)-2-cyano-3-(11-{[(1E)-(dimethylamino)methylene]amino}-7,8,9,10-tetrahydrocyclohepta[b]chromen-6-yl)acrylate. Both dyes in solution have a purple color with high extinction coefficients, but due to the different size of the partially saturated cycle, the first one displays fluorescence, and the second one does not. The fluorescence quantum yields for N'-(4-formyl-2,3-dihydro-1H-benzo[b]xanthen-12-yl)-N,N-dimethylimidoformamide decrease with decreasing solvent polarity. For example, the highest emission quantum yield is observed in methanol (2.76%), while the smallest is observed in tetrahydrofuran (1.04%). It is due to the fact that methanol implies a lesser energy consumption during the redistribution of electron density in the excited state. N'-[4-(2,2-dicyanovinyl)-2,3-dihydro-1H-benzo[b]xanthen-12-yl]-N,N-dimethylimidoformamide dye can be used as a fluorophore, whereas ethyl (2E)-2-cyano-3-(11-{[(1E)-(dimethylamino)methylene]amino}-7,8,9,10-tetrahydrocyclohepta[b]chromen-6-yl)acrylate dye can be used as a light filter to create a variety of materials and devices. In addition, the synthesized compounds can be used as building-blocks in organic chemistry.

Polarization Reorientation of Carbon Nitride Induced by a Local Bridge Donor for Boosting Photocatalytic H2 Evolution Integrated with Selective Amine Oxidation

Polymeric carbon nitride (PCN) has attracted much attention in the field of photocatalysis, but the use of PCN is often confined to internal structures with highly symmetrical heptazine units bridged by N atoms. Accurate tuning of the positions of heteronuclear atoms is a meaningful strategy but remains a big challenge. Herein, a catalyst with P═N bonds accurately embedded among the heptazine units was prepared using a straightforward polymerization method. According to density functional theory simulation and experimental data, the embedded P═N chains act as donor units that cause a profound redistribution of the symmetric electron cloud density of heptazine, which significantly promotes local charge polarization and leads to a strong built-in electric field. The consequence is enhanced exciton dissociation, charge separation, and surface activation. In the photocatalytic oxidation of benzylamine over the optimized PCN under visible light irradiation without the use of a solvent and co-catalyst, the hydrogen production rate is 388 μmol·g–1·h–1 and the selectivity to N-benzylidenebenzylamine is >99%. In this paper, we propose a tractable strategy to precisely tune the position of heteroatoms, providing an efficient catalyst for hydrogen production together with the simultaneous generation of value-added imines.

Insight into the effect of alloying on the adsorption of benzene on Ag(100) surface: DFT calculations

Heterogeneous catalysis, molecular sensors, and photovoltaics all rely on the interfaces between organic molecules and metal surfaces. Here, we study the adsorption of benzene on Ag(100) surface doped by Aun, Pdn, Ptn(n= 1–4), Au2Pd2, Au2Pt2 and Pd2Pt2 using density-functional theory (DFT), with the inclusion of van der Waals interactions, and compare with available computational and experimental result. The calculated quantities reveal that the interaction strength of Benzene with the surface gradually increases when it is doped by Pd or Pt atoms, showing a change in the nature of the interaction, from physisorption to chemisorption. We found that with surface allowing, one can tune the interaction strength. The charge transfer was found to occur from the molecule to the clean and doped surfaces with Au atoms and from the doped surface with Pd to the molecule. The redistribution of charge density indicates modifications in the features of the interface between the doped Ag(100) surfaces and benzene. In addition, alloying the Ag(100) surface with reactive TM changes substantially its electronic properties, which impacts its interactions with benzene. Finally, mixing two dopants or more can tune the electronic structure in designing more effective interfaces for various applications.

INFLUENCE OF A UNIFORM MAGNETIC FIELD ON THE GENERATION OF STRONG SMALL-SCALE MAGNETIC FIELDS DURING THE INJECTION OF A PLASMA WITH HOT ELECTRONS INTO AN INHOMOGENEOUS COLD PLASMA LAYER

We carry out a numerical modeling of plasma injection with hot electrons into a thin layer of cold plasma in the presence of an external magnetic field. We show that the latter can significantly affect the emerging small-scale current filaments and sheets, even if it does not magnetize the particles and does not change the overall dynamics of the redistribution of the total plasma density in the process of injection. The effect observed depends on the orientation of the external magnetic field that is parallel to the plane that bounds the cold plasma layer, if the injection occurs from a narrow strip lying in this plane. In this situation, which corresponds to the ablation of a flat target by a femtosecond laser beam using cylindrical focusing, we study the evolution of the characteristic structures of the formed small-scale magnetic field. It is established that its generation is associated with instabilities of the anisotropic velocity distribution of electrons, and its value can be many times greater than the value of the external magnetic field.

Oxygen-vacancy defect engineering to boost the aerobic oxidation of limonene over Co3O4 nanocubes

The heterogeneous aerobic oxidation of biomass-derived limonene under mild reaction conditions is an attractive target for the synthesis of valuable oxygenates, but qualifying catalyst represents an enormous challenge. Herein, we propose an oxygen-vacancy defect engineering strategy for steering the limonene oxidation catalysis over Co3O4 nanocubes. Comprehensive characterizations demonstrate that the incorporation of oxygen vacancy (Ov) in the Co3O4 structure triggers the redistribution of charge density and the modulation of Co chemical environment with the formation of more coordinated unsaturated Co atoms. Both the experimental findings and density functional theory (DFT) calculations explicitly evidence the boosting role of Ov in facilitating the radical initiation process, thereby substantially driving the generation of active radicals for the subsequent oxidation to proceed more feasibly. This work paves a way to structural microenvironment modulation induced by oxygen-vacancy defect engineering strategy towards high-performance limonene oxidation catalysis and beyond.

Electromigration Risk Assessment and Circuit Optimization using Innovative Multiphysics Modeling

With smaller and denser transistors, the physical flow of electrons may inhibit the performance of the device over time by forming voids and cracks at interconnects due to Electro-Migration (EM). Circuit designs that fail to meet EM specifications may lead to catastrophic failures and SI/PI performance degradation. One way of mitigating EM is to use multiple vias between layers of copper traces to reduce the current crowding effect. However, the quantities of vias may affect the current density and current redistribution inside critical joints. Current studies mainly focus on predicting the EM time-to-failure (TTF) based on the empirical Black’s equation. However, this method may not give enough insights about void formation and crack propagation and reflects the current redistribution that could impact the TTF. In this study, we compared the EM lifetime of Ball Grid Array (BGA) test vehicles with different structural designs and developed a methodology to consider the diffusion of atoms in solder joints based on Multiphysics field migration to study the current redistribution influence of vias. Moreover, crack propagation was also simulated to understand the failure mechanism. BGA traces without vias and with 8 vias are stressed under 5A, 7A, and 9A at 150C to compare the EM performance. Moreover, each test structure is manufactured with two different surface finishes: A and B. Based on the experimental results, Finite Element Analysis (FEA) simulations based on Atom Flux Divergence (AFD) were performed to compare with the experiment results. It was found that the current crowding effect could be significantly reduced by 8 vias compared to daisy chained traces. The study shows better EM resistance with 8 and 4 vias than no-via traces and helps predict the EM life of different structures to provide guidance for design optimization

Vertical strain engineering of Van der Waals heterostructures

Van der Waals materials and their interfaces play critical roles in defining electrical contacts for nanoelectronics and developing vehicles for mechanoelectrical energy conversion. In this work, we propose a vertical strain engineering approach by enforcing pressure across the heterostructures. First-principles calculations show that the in-plane band structures of 2D materials such as graphene, h-BN, and MoS2 as well as the electronic coupling at their contacts can be significantly modified. For the graphene/h-BN contact, a band gap in graphene is opened, while at the graphene/MoS2 interface, the band gap of MoS2 and the Schottky barrier height at contact diminish. Changes and transitions in the nature of contacts are attributed to localized orbital coupling and analyzed through the redistribution of charge densities, the crystal orbital Hamilton population, and electron localization, which yield consistent measures. These findings offer key insights into the understanding of interfacial interaction between 2D materials as well as the efficiency of electronic transport and energy conversion processes.

Nature of Interlayer Bonds in Two-Dimensional Materials

The role of interlayer bonds in the two-dimensional (2D) materials "beyond graphene" and so-called van der Waals heterostructures is vital, and understanding the nature of these bonds in terms of strength and type is essential due to a wide range of their prospective technological applications. However, this issue has not yet been properly addressed in the previous investigations devoted to 2D materials. In our work, by using first-principles calculations we perform a systematic study of the interlayer bonds and charge redistribution of several representative 2D materials that are traditionally referred as van der Waals systems. Our results demonstrate that one can distinguish three main types of inter-layer couplings in the considered 2D structures: one atom thick membranes bonded by London dispersion forces (graphene, hBN), systems with leading electrostatic interaction between layers (diselenides, InSe and bilayer silica) and materials with so-called dative or coordination chemical bonds between layers (ditelurides). We also propose a protocol for recognising the leading type of interlayer bonds in a system that includes comparison of interlayer distances, binding energies and redistribution of the charge densities in interlayer space. Such an approach is computationally cheap and can be used to further prediction of chemical and physical properties such as charge density waves (CDW), work function and chemical stability at ambient conditions.

Developmental loss of ErbB4 in PV interneurons disrupts state-dependent cortical circuit dynamics.

GABAergic inhibition plays an important role in the establishment and maintenance of cortical circuits during development. Neuregulin 1 (Nrg1) and its interneuron-specific receptor ErbB4 are key elements of a signaling pathway critical for the maturation and proper synaptic connectivity of interneurons. Using conditional deletions of the ERBB4 gene in mice, we tested the role of this signaling pathway at two developmental timepoints in parvalbumin-expressing (PV) interneurons, the largest subpopulation of cortical GABAergic cells. Loss of ErbB4 in PV interneurons during embryonic, but not late postnatal development leads to alterations in the activity of excitatory and inhibitory cortical neurons, along with severe disruption of cortical temporal organization. These impairments emerge by the end of the second postnatal week, prior to the complete maturation of the PV interneurons themselves. Early loss of ErbB4 in PV interneurons also results in profound dysregulation of excitatory pyramidal neuron dendritic architecture and a redistribution of spine density at the apical dendritic tuft. In association with these deficits, excitatory cortical neurons exhibit normal tuning for sensory inputs, but a loss of state-dependent modulation of the gain of sensory responses. Together these data support a key role for early developmental Nrg1/ErbB4 signaling in PV interneurons as a powerful mechanism underlying the maturation of both the inhibitory and excitatory components of cortical circuits.

Effects of trapped electrons on the sheath at the boundary of a dusty plasma

In the present paper, the characteristic behaviors of the sheath in an unmagnetized dusty plasma that contained trapped electrons, cold ions, and variable-charged dusts are investigated, based on the Sagdeev potential approach. The result shows that both the formation and structure of the sheath are modified by the trapped electrons. At the sheath edge, the critical ion Mach number decreases as the trapping parameter β increases. It is noted that the effect of electron trapping on the ion-entering-sheath-velocity is indirect, and closely related to the dust charge variation. In the sheath, the increased β leads to the enlargement of the sheath thickness and the absolute value of electrostatic potential, which results in the redistribution of particle densities. Moreover, the results of the Maxwellian case are essentially recovered when β = 1. As expected, the present results can give more insight into the interaction processes that happened on the plasma-wall interface.

On the mechanism of anomalous phenomena in current-carrying magnetized plasma

The explanation of the mechanisms of anomalous resistance and diffusion of plasma, as well as the generation of fast particles, is given from a unified position on the basis of experimental results obtained in plasma in a magnetically isolated diode of an electron accelerator with a microsecond pulse duration. It is shown that oscillations of the potential and current in plasma with current occur by charge separation and the formation of electric domains with a strong field. Electric domains are generated by means of runaway electrons resulting from the redistribution of the current density and its channelling in the current-carrying plasma. An increase in plasma resistance occurs due to a decrease in the number of electrons in the current-conducting state, since some of the plasma electrons pass into layers of excess negative charge of electric domains. The speed of movement of electrons in the composition of the electric domain is much lower than the velocity of electrons in the conducting state. The nucleation of domains is accompanied by microwave emission. Quasi-neutrals in whole electrical domains are injected into the region of the anode wall. The destruction of domains leads to the appearance of plasma channels between the anode and cathode plasma. The transverse electromagnetic waves generated during the nucleation of domains capture charged particles and inject them in a direction that is perpendicular to the insulating longitudinal magnetic field. Plasma turbulence occurs due to charge separation and the generation of electrical domains that create channels between the plasma and the chamber wall, as well as generating fluxes of fast particles.

3D reduced graphene oxide wrapped MoS2@Sb2S3 heterostructures for high performance sodium-ion batteries

Metal sulfides have been widely used as the anode materials of sodium-ion batteries (SIBs) due to their high theoretical capacity. However, their inherent low conductivity and irreversible volume expansion limit their electrochemical performance and application. To solve these problems, the MoS2@Sb2S3 heterostructure composites wrapped by 3D interconnected reduce graphene oxide (rGO) are prepared. The MoS2@Sb2S3 heterostructure accelerates the transfer of ions and electrons, and provides rich active sites, which facilitates electrolyte penetration and improves the interfacial reaction kinetics. Wrap 3D interconnected rGO networks around the porous MoS2@Sb2S3 composites to reduce the volume expansion of composite materials in the process of sodiumization and desodiumization, and ensure the structural stability. The theoretical calculation further supports the experimental results that the MoS2@Sb2S3/rGO heterojunction promotes the redistribution of different charge density and optimizes the adsorption energy of the composite for Na+, thus accelerating the electrochemical reaction kinetics. The MoS2@Sb2S3/rGO composite as the anode materials of SIBs can achieve a discharge specific capacity of 591.6 mAh g−1 at the second cycle with current density of 5 A g−1, and 162.1 mAh g−1 after 1100 cycles. High-rate capacities are achieved for SIBs (350.4 mAh g−1 @ 1 A g−1, 260.1 mAh g−1 @ 5 A g−1). This work provides a practical method for preparing anode materials of SIBs with excellent electrochemical performance.

Time-Resolved Chiral X-Ray Photoelectron Spectroscopy with Transiently Enhanced Atomic Site Selectivity: A Free-Electron Laser Investigation of Electronically Excited Fenchone Enantiomers

Chirality is widespread in nature, playing a fundamental role in biochemical processes and in the origin of life itself. The observation of dynamics in chiral molecules is crucial for the understanding and control of the chiral activity of photoexcited states. One of the most promising techniques for the study of photoexcited chiral systems is time-resolved photoelectron circular dichroism (TR-PECD), which offers an intense and sensitive probe for vibronic and geometric molecular structure as well as electronic structures, and their evolution on a femtosecond timescale. However, the nonlocal character of the PECD effect, which is imprinted during the electron scattering off the molecule, makes the interpretation of TR-PECD experiments challenging. In this respect, core photoionization is known to allow site and chemical sensitivity to photelectron spectroscopy. Here we demonstrate that TR-PECD utilizing core-level photoemission enables probing the chiral electronic structure and its relaxation dynamics with atomic site sensitivity. Following UV pumped excitation to a 3s Rydberg state, fenchone enantiomers (C10H16O) were probed on a femtosecond scale using circularly polarized soft x-ray light pulses provided by the free-electron laser FERMI. C 1s binding energy shifts caused by the redistribution of valence electron density in this 3s-valence-Rydberg excitation allowed us to measure transient PECD chiral responses with an enhanced C atom site selectivity compared to that achievable in the ground state molecule. This chemical-specific, site-specific, and enantiosensitive observation of the electronic structure of a transiently photoexcited chiral molecule is expected to pave the way toward chiral femtochemistry probed by core-level photoemission.Received 2 March 2022Revised 27 September 2022Accepted 2 February 2023DOI:https://doi.org/10.1103/PhysRevX.13.011044Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasChiralityElectronic structure of atoms & moleculesPhysical SystemsMoleculesTechniquesPhotoionizationUltrafast femtosecond pump probeX-ray photoelectron spectroscopyAtomic, Molecular & Optical