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The nitrogen-vacancy (NV) center is a promising candidate to realize practical quantum sensors with high sensitivity and high spatial resolution at room temperature and atmospheric pressure. In conventional high-frequency AC magnetometry with NV centers, the setup requires a pulse sequence with an appropriate time synchronization and strong microwave power. To avoid these practical difficulties, AC magnetometry using continuous-wave optically detected magnetic resonance (CW-ODMR) was recently demonstrated. That previous study utilized radio frequency (RF)-dressed states generated by the coherent interaction between the electron spin of the NV center and the RF wave. However, the drawback of this method is that the detectable frequency of the AC magnetic fields is fixed. Here, we propose and demonstrate frequency-tunable magnetic field sensing based on CW-ODMR. In the new sensing scheme, we obtain RF double-dressed states by irradiation with RF fields at two different frequencies. One creates the RF-dressed states and changes the frequency of the target AC field. The other is a target AC field that induces a change in the CW-ODMR spectrum by generating the RF double-dressed states through coherent interaction with the RF-dressed states. The sensitivity of our method is estimated to be comparable to or even higher than that of the conventional method based on the RF field with a single frequency. The estimated bandwidth is 7.5 MHz, higher than that of the conventional method using the RF-dressed states. Our frequency-tunable magnetic field sensor based on CW-ODMR paves the way for new applications in diamond devices. [ABSTRACT FROM AUTHOR]

Although it plays a critical role in the photophysics and catalysis of lanthanides, spin–orbit coupling of electrons on individual lanthanide atoms in small clusters is not well understood. The major objective of this work is to probe such coupling of the praseodymium (Pr) 4f and 6s electrons in Pr2O2 and Pr2O2+. The approach combines mass-analyzed threshold ionization spectroscopy and spin–orbit multiconfiguration second-order quasi-degenerate perturbation theory. The energies of six ionization transitions are precisely measured; the adiabatic ionization energy of the neutral cluster is 38 045 (5) cm−1. Most of the electronic states involved in these transitions are identified as spin–orbit coupled states consisting of two or more electron spins. The electron configurations of these states are 4f46s2 for the neutral cluster and 4f46s for the singly charged cation, both in planar rhombus-type structures. The spin–orbit splitting due to the coupling of the electrons on the separate Pr atoms is on the order of hundreds of wavenumbers. [ABSTRACT FROM AUTHOR]

Bio-spinterfaces present numerous opportunities to study spintronics across the biomolecules attached to (ferro)magnetic electrodes. While it offers various exciting phenomena to investigate, it is simultaneously challenging to make stable bio-spinterfaces as biomolecules are sensitive to many factors that it encounters during thin-film growth to device fabrication. The chirality-induced spin-selectivity effect is an exciting discovery, demonstrating an understanding that a specific electron's spin (either up or down) passes through a chiral molecule. The present work utilizes Ustilago maydis Rvb2 protein, an ATP-dependent DNA helicase (also known as Reptin), to fabricate bio-spintronic devices to investigate spin-selective electron transport through the protein. Ferromagnetic materials are well-known for exhibiting spin-polarization, which many chiral and biomolecules can mimic. We report herein spin-selective electron transmission through Rvb2 that exhibits 30% spin polarization at a low bias (+0.5 V) in a device configuration, Ni/Rvb2 protein/indium tin oxide measured under two different magnetic configurations. Our findings demonstrate that biomolecules can be put in circuit components without any expensive vacuum deposition for the top contact. The present study holds a remarkable potential to advance spin-selective electron transport in other biomolecules, such as proteins and peptides, for biomedical applications. [ABSTRACT FROM AUTHOR]

Molecular qubits are an emerging platform in quantum information science due to the unmatched structural control that chemical design and synthesis provide compared to other leading qubit technologies. This theoretical study investigates pulse sequence protocols for spin-correlated radical pairs, which are important molecular spin qubit pair (SQP) candidates. Here, we introduce improved microwave pulse protocols for enhancing the execution times of quantum logic gates based on SQPs. Significantly, this study demonstrates that the proposed pulse sequences effectively remove certain contributions from nuclear spin effects on spin dynamics, which are a common source of decoherence. Additionally, we have analyzed the factors that control the fidelity of the SQP spin state, following the application of the controlled-NOT gate. It was found that higher magnetic fields introduce a high frequency oscillation in the fidelity. Thereupon, it is suggested that further research should be geared toward executing quantum gates at lower magnetic field values. In addition, an absolute bound of the fidelity outcome due to decoherence is determined, which clearly identifies the important factors that control gate execution. Finally, examples of the application of these pulse sequences to SQPs are described. [ABSTRACT FROM AUTHOR]

The selectivity of multicarbon products in the CO2 reduction reaction (CO2RR) depends on the spin alignment of neighboring active sites, which requires a spin catalyst that facilitates electron transfer with antiparallel spins for enhanced C−C coupling. Here, we design a radical‐contained spin catalyst (TEMPOL@HKUST‐1) to enhance CO2‐to‐ethylene conversion, in which spin‐disordered (SDO) and spin‐ordered (SO) phases co‐exist to construct an asymmetric spin configuration of neighboring active sites. The replacement of axially coordinated H2O molecules with TEMPOL radicals introduces spin‐spin interactions among the Cu(II) centers to form localized SO phases within the original H2O‐mediated SDO phases. Therefore, TEMPOL@HKUST‐1 derived catalyst exhibited an approximately two‐fold enhancement in ethylene selectivity during the CO2RR at −1.8 V versus Ag/AgCl compared to pristine HKUST‐1. In situ ATR‐SEIRAS spectra indicate that the spin configuration at asymmetric SO/SDO sites significantly reduces the kinetic barrier for *CO intermediate dimerization toward the ethylene product. The performance of the spin catalyst is further improved by spin alignment under a magnetic field, resulting in a maximum ethylene selectivity of more than 50 %. The exploration of the spin‐polarized kinetics of the CO2RR provides a promising path for the development of novel spin electrocatalysts with superior performance. [ABSTRACT FROM AUTHOR]

As a fundamental degree of freedom, phonon chirality is expected to promote the development of quantum information technology just like electron spin. Currently, central to this area is the realization of efficient transmission and control of chiral information. In this paper, we propose an approach by integrating topological theory, leveraging topologically invariant Chern numbers, to encode hexagonal lattice systems. Our investigation reveals the presence of topologically protected chiral interface states within the shared band gaps of both trivial and non-trivial system units. By precisely modulating the magnetic field distribution within the encoding system, we can effectively manipulate the topological pathways. Building upon this framework, we design and implement a chiral phonon three-port device. Through dynamic calculations, we demonstrate the transmission process of chiral information, showcasing the chiral phonon switching effect and logical OR operation. Our findings not only establish a fundamental mechanism for the manipulation and control of phonon chiral information but also provide a promising direction for research in harnessing chirality degrees of freedom in practical applications. [ABSTRACT FROM AUTHOR]

Recently, a three dimensional metal-organic framework (MOF) based on Dy(III) and the L-tartrate ligand was experimentally shown to exhibit a spin polarization (SP) power of 100% at room temperature. The material's spin filtering ability was ascribed to the chiral-induced spin selectivity (CISS) effect. In this work, we computationally characterize the electronic structure of this MOF, revealing that the high SP of the material is linked to the asymmetric arrangement, around the Fermi level, of the alpha- and beta-spin electron states arising from the 4f-states of the lanthanide Dy atom, which results in two different conduction channels (band gaps) for each spin state. Based on the understanding gathered in this work, we propose that the substitution of the hydroxyl groups of the ligand by mercaptan groups should boost the electrical conductivity, while retaining the spin filtering power of the material. Recently ideal spin filtering ability was demonstrated in the Dy-L-Tar metal-organic framework. In this work the authors show that this unusual effect emerges from the asymmetric display of alpha and beta spin states around the Fermi level, composed of the f states of the lanthanide. [ABSTRACT FROM AUTHOR]

We propose the superconducting van der Waals material 4Hb-TaS2 to realize the Z 2 topological order and interpret the recent discovery of the spontaneous vortex generation in 4Hb-TaS2 as the vison-vortex nucleation. For the alternating stacking of metallic/superconducting and Mott insulating layers in 4Hb-TaS2, we expect the local moments in the Mott insulating 1T-TaS2 layer to form the Z 2 topological order. The spontaneous vortex generation in 4Hb-TaS2 is interpreted from the transition or nucleation between the superconducting vortex and the Z 2 vison in different phase regimes. Differing from the single vison-vortex nucleation in the original Senthil–Fisher's cuprate proposal, we consider such nucleation process between the superconducting vortex lattice and the vison crystal. We further propose experiments to distinguish this proposal with the Z 2 topological order from the chiral spin liquid scenarios. [ABSTRACT FROM AUTHOR]

Spin state switching in the metal center is a crucial phenomenon in many enzymatic reactions in biology. The spin state alteration, a critical step in cytochrome P450 catalysis, is driven most likely through a weak perturbation upon substrate binding in the enzyme, which is still not well clarified. In the current work, the spin state transition of iron(III) from high to intermediate via an admixed state is observed upon a subtle electronic perturbation to the sulphonate moieties coordinated axially to a diiron(III)porphyrin dimer. While electron‐donating substituents stabilize the high‐spin state of iron(III), strongly electron‐withdrawing groups stabilize an intermediate‐spin state, whereas the moderate electron‐withdrawing nature of axial ligands resulted in an admixed state. Confirmation of the molecular structures and their spin states have been made utilizing single‐crystal X‐ray structure analysis, Mössbauer, magnetic, EPR, and 1H NMR spectroscopic investigations. The position of the signals of the porphyrin macrocycle in the paramagnetic 1H NMR is found to be very characteristic of the spin state of the iron center in solution. The Curie plot for the pure high‐spin complexes shows the signals′ temperature dependency in line with the Curie law. Conversely, the pure intermediate‐spin state of iron exhibits an anti‐Curie temperature dependence, whereas the admixed‐spin state of iron displays significant curvature of the lines in the Curie plot. An extensive DFT analysis displays a linear dependence between the energy difference between dx2-y2 ${{_{x{^{2}}- y{^{2}}}}}$ and dz2 ${{_{z{^{2}}}}}$ orbital versus Fe−Npor distance for the complexes reported here. Furthermore, a strong linear correlation between the Fe−O distance and the spin density over the oxygen atom, as well as the Fe−Npor distance for the complexes, has been observed. Thus, a slight electronic perturbation at the axial ligand of the diheme resulted in a large change in the electronic structures with a spin‐flip. This is at par with the metalloenzymes, which employ minute perturbations around the periphery of the active sites, leading to spin state transitions. [ABSTRACT FROM AUTHOR]

The adsorption stability, geometry, and electronic and magnetic properties of H2S adsorbed on pristine, vacancy defected, and transition metal (TM)-doped phosphorene-graphene (PG) heterostructures were calculated using density functional theory. In pristine and vacancy defected PG systems, the interaction between H2S and the heterostructure was weak, and the mechanism was physical adsorption. After TM-doping (Ti, V, Cr, Mn, Co, and Ni), the strong orbital hybridisation between the dopant and H2S significantly enhanced the interaction between H2S and the doped heterostructures, and the physisorption mechanism of H2S changed to chemical adsorption. The adsorption energy and desorption time of H2S molecules on Mn-doped PG heterostructures was suitable, which can be applied as sensors to detect H2S gas. The density of states of Cr- and Mn-doped PG heterostructures exhibited asymmetric electron spin states, indicating the existence of magnetic moments. Thus, introducing defects and TM dopants on PG heterostructures can improve H2S sensitivity, providing a theoretical basis for developing gas detection sensors. [ABSTRACT FROM AUTHOR]

Photoexcitable donor–bridge–acceptor (D–B–A) molecules that support intramolecular charge transfer are ideal platforms to probe the influence of chiral induced spin selectivity (CISS) in electron transfer and resulting radical pairs. In particular, the extent to which CISS influences spin polarization or spin coherence in the initial state of spin-correlated radical pairs following charge transfer through a chiral bridge remains an open question. Here, we introduce a quantum sensing scheme to measure directly the hypothesized spin polarization in radical pairs using shallow nitrogen–vacancy (NV) centers in diamond at the single- to few-molecule level. Importantly, we highlight the perturbative nature of the electron spin–spin dipolar coupling within the radical pair and demonstrate how Lee–Goldburg decoupling can preserve spin polarization in D–B–A molecules for enantioselective detection by a single NV center. The proposed measurements will provide fresh insight into spin selectivity in electron transfer reactions. [ABSTRACT FROM AUTHOR]

Accurate prediction of a spin-state energy difference is crucial for understanding the spin crossover phenomena and is very challenging for density functional approximations, especially for local and semi-local approximations due to delocalization errors. Here, we investigate the effect of the self-interaction error removal from the local spin density approximation (LSDA) and Perdew–Burke–Ernzerhof generalized gradient approximation on the spin-state gaps of Fe(II) complexes with various ligands using recently developed locally scaled self-interaction correction (LSIC) by Zope et al. [J. Chem. Phys. 151, 214108 (2019)]. The LSIC method is exact for one-electron density, recovers the uniform electron gas limit of the underlying functional, and approaches the well-known Perdew–Zunger self-interaction correction (PZSIC) as a particular case when the scaling factor is set to unity. Our results, when compared with reference diffusion Monte Carlo results, show that the PZSIC method significantly overestimates spin-state gaps favoring low spin states for all ligands and does not improve upon density functional approximations. The perturbative LSIC-LSDA using PZSIC densities significantly improves the gaps with a mean absolute error of 0.51 eV but slightly overcorrects for the stronger CO ligands. The quasi-self-consistent LSIC-LSDA, such as coupled-cluster single double and perturbative triple [CCSD(T)], gives a correct sign of spin-state gaps for all ligands with a mean absolute error of 0.56 eV, comparable to that of CCSD(T) (0.49 eV). [ABSTRACT FROM AUTHOR]

[Display omitted] Radical-nonradical co-dominant pathways have become a hot topic in advanced oxidation, but achieving this on transition metal sulfides (TMS) remains challenging because their inherently higher electron and spin densities always induce radicals rather than nonradicals. Herein, a biosurfactant layer (BLR) was introduced to redistribute the electron and spin structure of nanoscale iron sulfide (FeS), which allowed both radical and nonradical to co-dominate the catalytic reaction. The resulting BLR-encased FeS hybrid (BLR@FeS) exhibited satisfactory removal efficiency (98.5 %) for hydrogen peroxide (H 2 O 2) activation, outperforming both the constituent components [FeS (70.9 %) and BLR (86.2 %)]. Advanced characterizations showed that C, O, N -related sites (−C O and −N C) in BLR attracted electrons in FeS due to their strong electronegativity and electron-withdrawing capacity, which not only decreased electron density in FeS, but also resulted in a shift of the Fe/S sites from the high-spin to the medium-spin state. The reaction routes established by the BLR@FeS/H 2 O 2 system maintained desirable stability against environmental interferences such as common inorganic anions, humic acid and changes in pH. Our study provides a state-of-the-art, molecule-level understanding of tunable co-dominant pathways and expands the targeted applications in the field of advanced oxidation. [ABSTRACT FROM AUTHOR]

This study outlines an effective method for improving the electrochemical properties of MoO 3 by tuning the electronic spin state of Mo via Ni doping, which can enhance its reactivity and weaken the diffusion energy barrier between Zn2+ and MoO 3. [Display omitted] • The electron spin states of Mo are modulated via Ni-ion doping. • The storage mechanism of this electron spin states tuning strategy is clarified. • The assembled Ni-MoO 3 //Zn can afford a high capacity of 258 mAh g −1 at 1 A/g. Aqueous zinc-ion batteries (AZIBs) have received considerable potential for their affordability and high reliability. Among potential cathodes, α-MoO 3 stands out due to its layered structure aligned with the (0 1 0) plane, offering extensive ionic insertion channels for enhanced charge storage. However, its limited electrochemical activity and poor Zn2+ transport kinetics present significant challenges for its deployment in energy storage devices. To overcome these limitations, we introduce a new strategy by doping α-MoO 3 with Ni (Ni-MoO 3), tuning the electron spin states of Mo. Thus modification can activate the reactivity of Ni-MoO 3 towards Zn2+ storage and weaken the interaction between Ni-MoO 3 and intercalated Zn2+, thereby accelerating the Zn2+ transport and storage. Consequently, the electrochemical properties of Ni-MoO 3 significantly surpass those of pure MoO 3 , demonstrating a specific capacity of 258 mAh g−1 at 1 A g−1 and outstanding rate performance (120 mAh g−1 at 10 A g−1). After 1000 cycles at 8 A g−1, it retains 76 % of the initial capacity, with an energy density of 154.4 Wh kg−1 and a power density of 11.2 kW kg−1. This work proves that the modulation of electron spin states in cathode materials via metal ion doping can effectively boost their capacity and cycling durability. [ABSTRACT FROM AUTHOR]

We introduce the combination of the density functional tight binding (DFTB) approach, including onsite correction (OC) and long-range corrected (LC) functional and the state-interaction state-averaged spin-restricted ensemble-referenced Kohn–Sham (SI-SA-REKS or SSR) method with extended active space involving four electrons and four orbitals [LC-OC-DFTB/SSR(4,4)], to investigate exciton couplings in multichromophoric systems, such as organic crystals and molecular aggregates. We employ the LC-OC-DFTB/SSR(4,4) method to calculate the excitonic coupling in anthracene and tetracene. As a result, the LC-OC-DFTB/SSR(4,4) method provides a reliable description of the locally excited (LE) state in a single chromophore and the excitonic couplings between chromophores with reasonable accuracy compared to the experiment and the conventional SSR(4,4) method. In addition, the thermal fluctuation of excitonic couplings from dynamic nuclear motion in an anthracene crystal with LC-OC-DFTB/SSR(4,4) shows a similar fluctuation of excitonic coupling and spectral density with those of first-principle calculations. We conclude that LC-OC-DFTB/SSR(4,4) is capable of providing reasonable features related to LE states, such as Frenkel exciton with efficient computational cost. [ABSTRACT FROM AUTHOR]

Magneto-intersubband resistance oscillations (MISOs) of highly mobile 2D electrons in symmetric GaAs quantum wells with two populated subbands are studied in magnetic fields B = (B ⊥ , B ∥) tilted from the normal to the 2D electron layer at different temperatures T. The in-plane component (B ∥) of the field B induces magnetic entanglement between subbands, leading to beating in oscillating density of states (DOS) and to MISO suppression. Model of the MISO suppression is proposed. Within the model, a comparison of MISO amplitude in the entangled and disentangled (B ∥ = 0) 2D systems yields both difference frequency of DOS oscillations, d f , and strength of the electron–electron interaction, described by parameter ε F ∗ , in the 2D system. These properties are analyzed using two methods, yielding consistent but not identical results for both d f and ε F ∗. The analysis reveals an additional angular dependent factor of MISO suppression. The factor is related to spin splitting of quantum levels in magnetic fields. [ABSTRACT FROM AUTHOR]

A NASICON‐type Mn/F dual‐doping Na4Fe3(PO4)2P2O7 cathode material is successfully synthesized via a spray drying method. A medium‐spin of Fe is measured by DFT calculation, X‐ray absorption near edge structure (XANES), temperature‐dependent magnetization susceptibility (M−T) measurement, and electron paramagnetic resonance (EPR) tests. It indicates that the eg orbital occupation of Fe2+ can be finely regulated, thus optimizing the bond strength between the oxidation and reduction processes. Furthermore, from UV−vis DRS and four‐point probe conductivity measurements, it can be seen that, after adjusting the electron spin states, the band gap of the material has decreased from 1.01 to 0.80 eV, and the electronic conductivity has increased from 8.5 to 24.4 µS cm−1, thereby leading to competitive electrochemical performance. The as‐optimized Na4Fe3(PO4)2P2O7 displays both excellent rate performance (121.0 and 104.9 mAh g−1 at 0.1 C and 5 C, respectively) and outstanding cycling stability (88.5% capacity retention after 1000 cycles at 1 C). The results indicate that this low‐cost Mn/F dual‐doping Na4Fe3(PO4)2P2O7 cathode can be a competitive candidate material for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

High-spin defect centers in crystal matrices are used in quantum computing technologies, highly sensitive sensors, and single-photon sources. In this work, optically active nitrogen-vacancy color centers NV– in a 28Si-enriched (nuclear spin ) 6H-28SiC crystal have been studied using the photoinduced ( = 980 nm) high-frequency (94 GHz, 3.4 T) pulsed electron paramagnetic resonance method at a temperature of K. Three structurally nonequivalent types of NV– centers with axial symmetry have been identified and their spectroscopic parameters have been determined. Long spin–lattice, ms, and spin–spin, μs, ensemble relaxation times of NV– centers with extremely narrow (450 kHz) absorption lines allow highly selective excitation of resonant transitions between sublevels caused by the weak hyperfine interaction MHz) with 14N nuclei for the quantum manipulation of the electron spin magnetization. [ABSTRACT FROM AUTHOR]

Covalent Organic Frameworks (COFs) demonstrate promising potential in the photocatalytic synthesis of H2O2 owing to favorable light absorption, superior charge separation, and considerable surface area. However, the efficiency of H2O2 photosynthesis is impeded by insufficient O2 adsorption sites and a high reaction barrier. In this work, various metal single atoms (Fe, Co, Ni) are introduced onto covalent triazine frameworks (CTFs) with N-N coordination sites to significantly enhance O2 adsorption and optimize H2O2 synthesis. Computational findings suggest that the presence of Fe, Co, and Ni not only enhances O2 adsorption but also exerts an influence on the reaction pathway of H2O2. Significantly, Fe exhibits a distinct advantage in modulating O2 adsorption through its unique electron spin state when compared to Co and Ni, as confirmed by crystal orbital Hamilton population (COHP) analysis. Additionally, this integration of metal atoms also improves light absorption and charge separation in CTFs. The study provides strategic insight into elevating H2O2 production by incorporating tailored metal single atoms into COFs. [ABSTRACT FROM AUTHOR]

The influence of the spin state of the metal centre in spin crossover compounds on the aromaticity of the ligands has been investigated for iron(II)tris-bipyridine (Fe(bpy)32+), and Fe(II)(formazanate)2 (as a truncated model and the full phenyl substituted compound). It was found that the aromaticity of the bipyridine ligands is unaffected by changing the spin state of the central iron atom, but that of the formazanate ligands is reduced upon transition to the high-spin state. This change in aromaticity is rationalized using the symmetry selection rules for aromaticity in terms of virtual excitations from occupied to empty orbitals. A further consequence of this loss in aromaticity is a shift to higher energy in the ring vibrations of the formazanate compounds that can be observed in either its IR or Raman spectrum; this prediction has been confirmed here. This change in aromaticity as a consequence of change in spin state can be regarded as an indication for non-innocent ligands. [ABSTRACT FROM AUTHOR]

Transitions in a system of interacting electron and nuclear spins in color centers with S = 3/2 in a 4H-SiC crystal with the natural isotopic composition have been detected by fully optical methods at room temperature. Giant changes in the photoluminescence in a volume of about 1 μm3 under cw and pulsed laser excitation occur in the region of the anticrossing of electron and nuclear spin levels. An optical manifestation of the flip of the nuclear spin of the 29Si isotope with the conservation of the projection of the electron spin has been detected. All anticrossing points of the spin sublevels coupled by hyperfine interactions have been identified. This identification enables the observation of such effects in the family of quarter spin centers in other SiC polytypes. [ABSTRACT FROM AUTHOR]

We present a theory for studying the quantum dynamics of both the transmission and reflection behavior of a two-dimensional electron gas across a planar potential step within a quantum well. In our model, we introduce the combined effect of the Rashba–Zeeman coupling on the conduction electrons. Our results demonstrate that as the energy of an incident or a transmitted electron stays within the Zeeman energy gap, both Klein reflection and Klein tunneling occur in this Rashba–Zeeman coupled electronic system, where the former corresponds to a backward spin filter while the latter to a forward spin filter. Meanwhile, our system also predicts a critical incident angle beyond which the electron tunneling will be fully suppressed. Such distinctive spin-filtering features are expected to give rise to a variety of applications in both spintronics and quantum-computation devices. [ABSTRACT FROM AUTHOR]

Heavy element compounds with high symmetries often feature both spin–orbit coupling and vibronic coupling. This is especially true for systems with tetrahedral and octahedral symmetries, whose electronic states may be threefold degenerate and experience complicated Jahn–Teller and pseudo-Jahn–Teller interactions. To accurately describe these interactions, high quality spin–orbit vibronic Hamiltonian operators are needed. In this study, we present a unified one-electron Hamiltonian formalism for spin–orbit vibronic interactions for systems in all tetrahedral and octahedral symmetries. The formalism covers all spin–orbit Jahn–Teller and pseudo-Jahn–Teller problems in the symmetries with arbitrary types and arbitrary numbers of vibrational modes and generates Hamiltonian expansion formulas of arbitrarily high order. [ABSTRACT FROM AUTHOR]

To establish a correlation between spin diffusion, spin lifetime, and electron density, we study spin polarization evolution in low-dimensional GaAs semiconductors hosting two-dimensional electron gases by employing time-resolved magneto-optical Kerr effect microscopy. It is shown that for the establishment of the longest spin-lifetime, the variation in the scattering rate with electron density is of more importance than fulfilling the persistent spin helix condition when the Rashba α and Dresselhaus β parameters are balanced. More specifically, regardless of α and β linear dependencies on the electron density, the spin relaxation rate is determined by the spin diffusion coefficient that depends on electron density nonmonotonously. The longest experimental spin-lifetime occurs at an electron density, corresponding to transition from Boltzmann to Fermi–Dirac statistics, which is several times higher than that when the persistent spin helix is expected. These facts highlight the role the electron density may play when considering applications for spintronic devices. [ABSTRACT FROM AUTHOR]

Algebraic diagrammatic construction (ADC) theory is a computationally efficient and accurate approach for simulating electronic excitations in chemical systems. However, for the simulations of excited states in molecules with unpaired electrons, the performance of ADC methods can be affected by the spin contamination in unrestricted Hartree–Fock (UHF) reference wavefunctions. In this work, we benchmark the accuracy of ADC methods for electron attachment and ionization of open-shell molecules with the UHF reference orbitals (EA/IP-ADC/UHF) and develop an approach to quantify the spin contamination in charged excited states. Following this assessment, we demonstrate that the spin contamination can be reduced by combining EA/IP-ADC with the reference orbitals from restricted open-shell Hartree–Fock (ROHF) or orbital-optimized Møller–Plesset perturbation (OMP) theories. Our numerical results demonstrate that for open-shell systems with strong spin contamination in the UHF reference, the third-order EA/IP-ADC methods with the ROHF or OMP reference orbitals are similar in accuracy to equation-of-motion coupled cluster theory with single and double excitations. [ABSTRACT FROM AUTHOR]

We theoretically explore the effect of a δ -potential on spin-polarized dwell time for electron in a magnetic nanostructure, which can be achieved by depositing a vertically-magnetized ferromagnetic stripe on top of InAs/AlxIn 1 − x As. The dwell time is found to be still spin-polarized because the δ -potential does not eliminate the spin-field interaction in the magnetic nanostructure. Spin-polarized dwell time is also found to be controllable by changing weight or position of the δ -potential since the effective potential experienced by electron in the magnetic nanostructure depends on the δ -potential. Therefore, such a δ -doped, magnetic nanostructure can act as a structurally-manipulable temporal spin splitter for spintronic device applications. [ABSTRACT FROM AUTHOR]

The cytochrome P450 family consists of ubiquitous monooxygenases with the potential to perform a wide variety of catalytic applications. Among the members of this family, CYP116B5hd shows a very prominent resistance to peracid damage, a property that makes it a promising tool for fine chemical synthesis using the peroxide shunt. In this meticulous study, we use hyperfine spectroscopy with a multifrequency approach (X- and Q-band) to characterize in detail the electronic structure of the heme iron of CYP116B5hd in the resting state, which provides structural details about its active site. The hyperfine dipole–dipole interaction between the electron and proton nuclear spins allows for the locating of two different protons from the coordinated water and a beta proton from the cysteine axial ligand of heme iron with respect to the magnetic axes centered on the iron. Additionally, since new anti-cancer therapies target the inhibition of P450s, here we use the CYP116B5hd system—imidazole as a model for studying cytochrome P450 inhibition by an azo compound. The effects of the inhibition of protein by imidazole in the active-site geometry and electron spin distribution are presented. The binding of imidazole to CYP116B5hd results in an imidazole–nitrogen axial coordination and a low-spin heme FeIII. HYSCORE experiments were used to detect the hyperfine interactions. The combined interpretation of the gyromagnetic tensor and the hyperfine and quadrupole tensors of magnetic nuclei coupled to the iron electron spin allowed us to obtain a precise picture of the active-site geometry, including the orientation of the semi-occupied orbitals and magnetic axes, which coincide with the porphyrin N-Fe-N axes. The electronic structure of the iron does not seem to be affected by imidazole binding. Two different possible coordination geometries of the axial imidazole were observed. The angles between gx (coinciding with one of the N-Fe-N axes) and the projection of the imidazole plane on the heme were determined to be −60° and −25° for each of the two possibilities via measurement of the hyperfine structure of the axially coordinated 14N. [ABSTRACT FROM AUTHOR]

Dye-decolorizing peroxidases (DyPs) are heme proteins with distinct structural properties and substrate specificities compared to classical peroxidases. Here, we demonstrate that DyP from the extremely radiation-resistant bacterium Deinococcus radiodurans is, like some other homologues, inactive at physiological pH. Resonance Raman (RR) spectroscopy confirms that the heme is in a six-coordinated-low-spin (6cLS) state at pH 7.5 and is thus unable to bind hydrogen peroxide. At pH 4.0, the RR spectra of the enzyme reveal the co-existence of high-spin and low-spin heme states, which corroborates catalytic activity towards H2O2 detected at lower pH. A sequence alignment with other DyPs reveals that DrDyP possesses a Methionine residue in position five in the highly conserved GXXDG motif. To analyze whether the presence of the Methionine is responsible for the lack of activity at high pH, this residue is substituted with a Glycine. UV-vis and RR spectroscopies reveal that the resulting DrDyPM190G is also in a 6cLS spin state at pH 7.5, and thus the Methionine does not affect the activity of the protein. The crystal structures of DrDyP and DrDyPM190G, determined to 2.20 and 1.53 Å resolution, respectively, nevertheless reveal interesting insights. The high-resolution structure of DrDyPM190G, obtained at pH 8.5, shows that one hydroxyl group and one water molecule are within hydrogen bonding distance to the heme and the catalytic Asparagine and Arginine. This strong ligand most likely prevents the binding of the H2O2 substrate, reinforcing questions about physiological substrates of this and other DyPs, and about the possible events that can trigger the removal of the hydroxyl group conferring catalytic activity to DrDyP. [ABSTRACT FROM AUTHOR]

Coherent spin dynamics of electrons in CdSe colloidal nanoplatelets are investigated by time-resolved pump–probe Faraday rotation at room and cryogenic temperatures. We measure electron spin precession in a magnetic field and determine g-factors of 1.83 and 1.72 at low temperatures for nanoplatelets with a thickness of 3 and 4 monolayers, respectively. The dephasing time of spin precession T 2 * amounts to a few nanoseconds and has a weak dependence on temperature, while the longitudinal spin relaxation time T 1 exceeds 10 ns even at room temperature. Observations of single and double electron spin–flips confirm that the nanoplatelets are negatively charged. The spin–flip Raman scattering technique reveals g-factor anisotropy by up to 10% in nanoplatelets with thicknesses of 3, 4, and 5 monolayers. In the ensemble with a random orientation of nanoplatelets, our theoretical analysis shows that the measured Larmor precession frequency corresponds to the in-plane electron g-factor. We conclude that the experimentally observed electron spin dephasing and its acceleration in the magnetic field are not provided by the electron g-factor anisotropy and can be related to the localization of the resident electrons and fluctuations of the localization potential. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) topological insulators (TIs) exhibit spin-polarized surface states in which the spin of electrons is locked to their momentum. The helical surface states can be explored from circularly polarized light-induced spin photocurrent, a phenomenon called circular photogalvanic effect (CPGE). In this work, we fabricate a TI transistor with the Bi2Se3 channel layer synthesized using vapor deposition. The photocurrent response of Bi2Se3 TI is characterized under horizontal and longitudinal electric fields. CPGE and linear photogalvanic effect (LPGE) contribute to the surface state photocurrent at room temperature. The longitudinal electric field provides kinetic energy to the electrons so that the transition of electrons to higher energy bands in momentum space occurs. Under a photon excitation with the energy far above the TI bandgap, we observed a photocurrent difference between left and right circularly polarized light excitation. The photocurrent variation with gate voltage (longitudinal field) is also investigated. Adjusting the Fermi level with the gate bias leads to changes in the population of bulk state carriers and spin electrons in surface states. By shifting the gate bias toward negative, the CPGE current increases because of the reduced scattering with bulk carriers. Our work reveals that longitudinal and horizontal electric fields can manipulate the helical spin-polarized photocurrent of Bi2Se3. From the asymmetry of circularly polarized photoconductive differential current (CPDC) under the horizontal field, we found evidence of spin-polarized electron transition to other conduction band valleys at room temperature under a high-energy photon excitation. [ABSTRACT FROM AUTHOR]

In this report, we revisit coherent spin exchange scattering experiments with low-energy electrons by Ni2+ ions in antiferromagnetic (AF) crystal NiO. The use of the advanced low-energy electron diffraction (LEED) technique for surface analysis enables more quantitative characterization of surface atoms of Ni2+ ions based on (1) the energy dependence of LEED for "half-order beam" intensity, i.e., the I–V curve, and (2) the temperature dependence at the intensity maximum of 31 eV. In the I–V curve, resonance enhancement is clearly observed, which corresponds to a surface wave resonance (SWR) effect. Under SWR conditions, i.e., the emergence of diffracted beams propagating nearly parallel to the crystal surface, the surface-spin structure properties are investigated through the low-temperature range where the saturation phenomenon can be confirmed. Those energy dependences are also calculated by the relativistic multiple-scattering method, and the temperature dependence is compared with a molecular field model. [ABSTRACT FROM AUTHOR]

The effective mass at the Fermi level is measured in the strongly interacting two-dimensional (2D) electron system in ultra-clean SiGe/Si/SiGe quantum wells in the low-temperature limit in tilted magnetic fields. At low electron densities, the effective mass is found to be strongly enhanced and independent of the degree of spin polarization, which indicates that the mass enhancement is not related to the electrons' spins. The observed effect turns out to be universal for silicon-based 2D electron systems, regardless of random potential, and cannot be explained by existing theories. [ABSTRACT FROM AUTHOR]

Waves exhibit unique characteristics, such as diffraction and interference, which distinguishes them from the particle nature of electrons currently used for binary and sequential data processing and storage. In the solid state, wave properties can be found in electron spin waves in semiconductors or magnons in magnetic materials. These are useful for communication, processing and storage, and allow multiplexing of the information. Given this perspective, after introducing the information theory of wave-parallel computing and arguing the fundamental properties necessary for implementation with wave-based information carriers, we specifically examine how electron spin waves and magnons can be used as information carriers for processing and storage. Then, after explaining the fundamental physics of the electron spin wave based on the persistent spin helix state, we assess the potential of magnon-assisted magnetization switching for realizing the selective writing and reading of multiplexed information. Ferromagnet/semiconductor hybrid structures are emphasized as a platform for generating and controlling both electron spin waves and magnons. Interconversion among light helicity, electron spin waves and magnons is also discussed. Finally, we show several challenges and provide an outlook on the key steps that must be demonstrated for implementing spin-based wave-parallel computing. [ABSTRACT FROM AUTHOR]

In addition to the fact that waves have been proven in different plasma environments, they have also been investigated under different physical regimes. In this research, the propagation of electromagnetic waves in quantum semiconductor plasma in the presence of a uniform external magnetic field was investigated using the quantum hydro magnetism model. The researches that have been done so far about these waves have mostly been done in classical or relativistic regimes. Some cases have been studied to study linear waves in quantum plasma, taking into account the quantum Bohm potential without investigating the effect of the spin characteristics of plasma particles. In addition to the simultaneous study of spin and quantum effects of semiconductor plasma components, exchange-correlation relationships have not been found in any research, and the most important novelty of the present work can be considered the addition of these relationships together. The obtained results show that the effects of quantum and external magnetic fields have a significant effect on the scattering of hydromagnetic waves, which causes the appearance of nonlinear terms in the scattering relationship. By increasing the linear part of the electron spin in the sputtering relation, some relations have been modified, including the Alfven velocity. On the other hand, the effect of electron spin leads to the reduction of the effect of other quantum potentials on the scattering of waves. In the end, some special states of classical and quantum systems are also discussed. Considering the limit states, the results of the present work are exactly similar to the results of other researchers, and this can be a self-confirmation of the obtained results. [ABSTRACT FROM AUTHOR]

Individual electron–nuclear spin systems in solids are promising platforms for implementation of second-generation quantum technologies. The recognized leader among such systems is the negatively charged nitrogen–vacancy color center (NV center) in diamond with hyperfine coupling to nuclear spins of carbon-13 (13C), which are widely used as a quantum memory in emerging quantum technologies because of their weak interaction with the environment. Recently, pairs of 13C–13C nuclei (dimers) in diamond with NV centers have been proposed and actively studied for this purpose because they have extremely long coherence times (minutes at room temperature) in the singlet state. The eigenstates of the spin Hamiltonian of the NV–13C–13C system were found and used to calculate the probabilities of EPR transitions between nuclear-spin sublevels of NV-center states with electron spin projections mS = 0 and mS = –1. The obtained expressions form the basis for choosing the optimal parameters of microwave and radiofrequency pulses transforming a particular dimer into the singlet state. An example of such a prediction for a specific NV–13C–13C spin system using data for the spatial positions of the 13C spins and the internal spin–spin couplings obtained earlier by quantum chemistry methods is presented. [ABSTRACT FROM AUTHOR]

The chiral molecules are potential generators of high spin-filters due to their inherent inversion asymmetric helical electric field. We report a controlled spin-selective transmission of electrons through self-assembled monolayers of 15 base-paired double-stranded deoxyribonucleic acid functionalized with two enantiomeric cysteine molecules on gold explored through the quantum mechanical tunneling effect. We observed a controlled spin polarization of 33% with dextro-cysteine, whereas a mere 8% was observed with levo-cysteine molecules using these functionalizations at room temperature. The manipulation of electron's spin merely through such a small molecule could lead to significant advancement in the spin-dependent charge transport phenomena and related applications. [ABSTRACT FROM AUTHOR]

The choice of substrate orientation for semiconductor quantum dot circuits offers opportunities for tailoring spintronic properties such as g-factors for specific functionality. Here, we demonstrate the operation of a few-electron double quantum dot circuit fabricated from a (110)-oriented GaAs quantum well. We estimate the in-plane electron g-factor from the profile of the enhanced inter-dot tunneling (leakage) current near-zero magnetic field. Spin blockade due to Pauli exclusion can block inter-dot tunneling. However, this blockade becomes inactive due to hyperfine interaction mediated spin flip-flop processes between electron spin states and the nuclear spin of the host material. The g-factor of absolute value ∼0.1 found for a magnetic field parallel to the direction [ 1 ¯ 10 ] is approximately a factor of four lower than that for comparable circuits fabricated from a material grown on widely employed standard (001) GaAs substrates and is in line with reported values determined by purely optical means for quantum well structures grown on (110) GaAs substrates. [ABSTRACT FROM AUTHOR]

The role of chirality in determining the spin dynamics of photoinduced electron transfer in donor-acceptor molecules remains an open question. Although chirality-induced spin selectivity (CISS) has been demonstrated in molecules bound to substrates, experimental information about whether this process influences spin dynamics in the molecules themselves is lacking. Here we used time-resolved electron paramagnetic resonance spectroscopy to show that CISS strongly influences the spin dynamics of isolated covalent donor–chiral bridge–acceptor (D-Bc-A) molecules in which selective photoexcitation of D is followed by two rapid, sequential electron-transfer events to yield D•+-Bc-A•–. Exploiting this phenomenon affords the possibility of using chiral molecular building blocks to control electron spin states in quantum information applications. [ABSTRACT FROM AUTHOR]

The effective mass at the Fermi level is measured in the strongly interacting two-dimensional (2D) electron system in ultra-clean SiGe/Si/SiGe quantum wells in the low-temperature limit in tilted magnetic fields. At low electron densities, the effective mass is found to be strongly enhanced and independent of the degree of spin polarization, which indicates that the mass enhancement is not related to the electrons' spins. The observed effect turns out to be universal for silicon-based 2D electron systems, regardless of random potential, and cannot be explained by existing theories. [ABSTRACT FROM AUTHOR]

• Characterizing the heterogeneity in intrinsically disordered protein ensembles is vital for understanding their function. • The NMR of IDPs is challenging because of poor spectral dispersion and severe resonance overlap. • We integrate spin-state-selective CEST and triple resonance coherence transfer to design a pulse sequence for measuring 1Hα excited state chemical shifts. • The pulse sequence is used for measuring excited state shifts in the intrinsically disordered DNA binding domain of the cytidine repressor (CytRN) • The structure of the CytRN excited state calculated from the 1Hα chemical shifts is a three-helix bundle with a helix-turn-helix motif. Over 40% of eukaryotic proteomes and 15% of bacterial proteomes are predicted to be intrinsically disordered based on their amino acid sequence. Intrinsically disordered proteins (IDPs) exist as heterogeneous ensembles of interconverting conformations and pose a challenge to the structure–function paradigm by apparently functioning without possessing stable structural elements. IDPs play a prominent role in biological processes involving extensive intermolecular interaction networks and their inherently dynamic nature facilitates their promiscuous interaction with multiple structurally diverse partner molecules. NMR spectroscopy has made pivotal contributions to our understanding of IDPs because of its unique ability to characterize heterogeneity at atomic resolution. NMR methods such as Chemical Exchange Saturation Transfer (CEST) and relaxation dispersion have enabled the detection of 'invisible' excited states in biomolecules which are transiently and sparsely populated, yet central for function. Here, we develop a 1Hα CEST pulse sequence which overcomes the resonance overlap problem in the 1Hα-13Cα plane of IDPs by taking advantage of the superior resolution in the 1H-15N correlation spectrum. In this sequence, magnetization is transferred after 1H CEST using a triple resonance coherence transfer pathway from 1Hα (i) to 1HN(i + 1) during which the 15N(t 1) and 1HN(t 2) are frequency labelled. This approach is integrated with spin state-selective CEST for eliminating spurious dips in CEST profiles resulting from dipolar cross-relaxation. We apply this sequence to determine the excited state 1Hα chemical shifts of the intrinsically disordered DNA binding domain (CytRN) of the bacterial cytidine repressor (CytR), which transiently acquires a functional globally folded conformation. The structure of the excited state, calculated using 1Hα chemical shifts in conjunction with other excited state NMR restraints, is a three-helix bundle incorporating a helix-turn-helix motif that is vital for binding DNA. [ABSTRACT FROM AUTHOR]

This work proposes a strategy to tailor the electron spin states of dual-metal-atom Fe 2 N 5 via the introduction of neighboring single-metal-atom NiN 4 sites, which enables it with superior ORR activities and ultralow HO 2 − yield that could avoid the occurrence of Fenton reaction, thus hitting the spot of ultra-long-term stability over 1200h for ZABs. [Display omitted] Breakthrough in developing cost-effective Fe-based catalysts with superior oxygen reduction reaction (ORR) activities and ultra-long-term stability for application in Zn-air batteries (ZABs) remain a priority but still full of challenges. Herein, the neighboring NiN 4 single-metal-atom and Fe 2 N 5 dual-metal-atoms on the N-doped hollow carbon sphere (Fe/Ni-NHCS) were deliberately constructed as the efficient and robust ORR catalyst for ZABs. Both theory calculations and magnetic measurements demonstrate that the introduction of NiN 4 provides a significant role on optimizing the electron spin state of Fe 2 N 5 sites and reducing the energy barrier for the adsorption and conversion of the oxygen-containing intermediates, enabling the Fe/Ni-NHCS with excellent ORR performance and ultralow byproduct HO 2 − yield (0.5%). Impressively, the ZABs driven by Fe/Ni-NHCS exhibit unprecedented long-term rechargeable stability over 1200 h. This work paves a new venue to manipulate the spin state of active sites for simultaneously achieving superior catalytic activities and ultra-long-term stability in energy conversion technologies. [ABSTRACT FROM AUTHOR]

The processing and analysis of synchrotron data can be a complex task, requiring specialized expertise and knowledge. Our previous work addressed the challenge of X-ray emission spectrum (XES) data processing by developing a standalone application using unsupervised machine learning. However, the task of analyzing the processed spectra remains another challenge. Although the non-resonant Kβ XES of 3d transition metals are known to provide electronic structure information such as oxidation and spin state, finding appropriate parameters to match experimental data is a time-consuming and labor-intensive process. Here, a new XES data analysis method based on the genetic algorithm is demonstrated, applying it to Mn, Co and Ni oxides. This approach is also implemented as a standalone application, Argonne X-ray Emission Analysis 2 (AXEAP2), which finds a set of parameters that result in a high-quality fit of the experimental spectrum with minimal intervention. AXEAP2 is able to find a set of parameters that reproduce the experimental spectrum, and provide insights into the 3d electron spin state, 3d-3p electron exchange force and Kβ emission core-hole lifetime. [ABSTRACT FROM AUTHOR]

In the present work, an S-HGMS coupling acid leaching technology was established to prepare high-purity silica using vein quartz ore. Firstly, the magnetic properties of different phases in vein quartz were investigated through density functional theory (DFT) calculations and arranged the phases in terms of magnetic susceptibility: FeP 2 > Al 2 SiO 5 > SiO 2 > Ca(Al 2 Si 2)O 8 > AlPO 4. Those differences in magnetic susceptibility resulted from the spin state of electrons in the ions. After treatment using the S-HGMS process, weakly magnetic particles are effectively separated from silica particles, and the obtained silica concentrate contained SiO 2 of 99.690% purity. Subsequently, lattice impurity ions were removed through a fluorine-free and low-fluoric acid leaching process. Under optimal conditions, the SiO 2 purity in high-purity silica reached 99.954% and 99.990% in the two processes. The lattice parameters and volume of ɑ-quartz in high-purity silica obtained with low-fluoric acid leaching were less than those obtained with fluorine-free acid leaching. This difference can be attributed to the reaction between HF molecules and lattice impurity ions, resulting in the generation of coordination compounds. Meanwhile, HF dissolved SiO 2 and opened the lattice impurity ions channel, promoting lattice impurity ions depth removal. This study established a complete set of critical technologies for preparing high-purity silica from vein quartz through the S-HGMS coupling acid leaching process, providing theoretical and scientific bases for industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Perovskite oxides are able to realize pseudocapacitive energy storage through oxygen anion intercalation. Herein, it is demonstrated that, based on the three 2H‐perovskite related oxides Sr6Co5O15‐x, Sr5Co4O12‐x, and Sr5Co3NiO12‐x as the research objects, metal oxyhydroxides generated through surface reconfiguration during electrochemical processes can contribute extra capacity besides the oxygen‐anion intercalation. This is because the electron spin state controlled by the transition metal valence state in the pseudo trigonal prisms for the 2H‐perovskite structure will affect the Jahn–Teller (JT) distortion. The strong JT distortion of Co2+ and Ni3+ would elongate metal‐O bonds, thereby helping the formation of metal oxyhydroxides on the surface of the pristine material. Among the three 2H‐perovskite related oxides, the specific capacity of Sr5Co3NiO12‐x having the most Co2+ and Ni3+ contents showed the highest capacity increase. This study will provide a promising pathway to develop advanced perovskite‐like oxide pseudocapacitive materials. [ABSTRACT FROM AUTHOR]

Altermagnetism can achieve spin-split bands in collinear symmetry-compensated antiferromagnets. Here, we predict altermagnetic order in Janus monolayer Cr2SO with eliminated inversion symmetry, which can realize the combination of piezoelectricity and altermagnetism in a two-dimensional (2D) material, namely, 2D piezoelectric altermagnetism. It is found that Cr2SO is an altermagnetic semiconductor, and the spin-split bands of both valence and conduction bands are near the Fermi level. The Cr2SO has large out-of-plane piezoelectricity ( | d 31 | = 0.97 pm/V), which is highly desirable for ultrathin piezoelectric device application. Due to spin-valley locking, both spin and valley can be polarized by simply breaking the corresponding crystal symmetry with uniaxial strain. Our findings provide a platform to integrate spin, piezoelectricity, and valley in a single material, which is useful for multi-functional device applications. [ABSTRACT FROM AUTHOR]

Rare‐earth (RE) elements have emerged as crucial promoters to regulate the electrocatalysis of transition metals (TM), but knowledge about the RE‐enhanced mechanism of TM in electrocatalysis is limited. Herein, an array‐like Ce‐CoP catalyst is constructed to explore the origin and distinction of the Ce‐induced enhanced mechanism of Co sites in both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Compared with individual CoP, the developed Ce‐CoP exhibits superior bifunctional electrocatalytic activity with the overpotentials of 81 and 240 mV at 10 mA cm−2, respectively for HER and OER, with excellent electrocatalytic stability. Theoretical calculations show that the unique 4f valence electron structure of Ce endows the Co sites with differentiated regulation in the HER and OER through f‐p‐d gradient orbital coupling. In the HER, the retained Ce‐4f state induces electron spin parallelism at the surrounding Co sites, promoting the adsorption of *H intermediates. While in the OER, the Ce‐4f band acts as sacrificing band to protect the Co sites from overoxidation through the Ce‐O‐Co chain with an optimized Co‐3d state, providing additional spin coupling with oxygen intermediates. These findings provide new insights into comprehending the RE‐enhanced mechanism of electrocatalysis and present valuable design guidelines for the development of efficient multi‐functional electrocatalysts. [ABSTRACT FROM AUTHOR]

We have improved a polarized electron source in which unpolarized electrons undergo collisions with a mixture of buffer gas molecules and optically spin-polarized Rb atoms. With a nitrogen buffer gas, the source reliably provides spin polarization between 15% and 25% with beam currents >4 μA. Vacuum pump upgrades mitigate problems caused by denatured diffusion pump oil, leading to longer run times. A new differential pumping scheme allows the use of higher buffer gas pressures up to 800 mTorr. With a new optics layout, the Rb polarization is continuously monitored by a probe laser and improved pump laser power provides more constant high polarization. We have implemented an einzel lens to better control the energy of the electrons delivered to the target chamber and to preferentially select electron populations of higher polarization. The source is designed for studies of biologically relevant chiral molecule samples, which can poison photoemission-based GaAs polarized electron sources at very low partial pressures. It operates adjacent to a target chamber that rises to pressures as high as 10−4 Torr and has been implemented in a first experiment with chiral cysteine targets. [ABSTRACT FROM AUTHOR]

Possible isomers of the N-(3,4-dimethylphenyl)-2-[(7-hydroxy-3′,3′-dimethyl-3′H-spiro[chromene-2,1′-isobenzofuran]-8-yl)methylidine]hydrazinocarbothioamide (HL) spiropyran of the 2-oxaindane series and the [ML(H2O)3]+ (M = Mn(II), Fe(II), Co(II)) complexes on its basis are calculated by the quantum chemical DFT (CAM-B3LYP/6-311++G(d,p)) method. It is shown that complexation inverts the relative stability of spiro- and acyclic isomers of L; the acyclic isomer of the ligand is the most stable one among all the complexes for all metals. The effect of ligand structural isomerism on the relative stability of high- and low-spin states of coordination compounds is estimated. [ABSTRACT FROM AUTHOR]

In 1921, Otto Stern conceived the idea for an experiment that would decide between a classical and a quantum description of atomic behavior, as epitomized by the Bohr–Sommerfeld–Debye model of the atom. This model entailed not only the quantization of the magnitude of the orbital electronic angular momentum but also of the projection of the angular momentum on an external magnetic field – the so‐called space quantization. Stern recognized that space quantization would have observable consequences: namely, that the magnetic dipole moment due to the orbital angular momentum would be space quantized as well, taking two opposite values for atoms whose only unpaired electron has just one quantum of orbital angular momentum. When acted upon by a suitable inhomogeneous magnetic field, a beam of such atoms would be split into two beams consisting of deflected atoms with opposite projections of the orbital angular momentum on the magnetic field. In contradistinction, if atoms behaved classically, the atomic beam would only broaden along the field gradient and have maximum intensity at zero deflection, i. e., where there would be a minimum or no intensity for a beam split due to space quantization. Stern anticipated that, although simple in principle, the experiment would be difficult to carry out – and invited Walther Gerlach to team up with him. Gerlach's realism and experimental skills together with his sometimes stubborn determination to make things work proved invaluable for the success of the Stern–Gerlach experiment (SGE). After a long struggle, Gerlach finally saw, on 8 February 1922, the splitting of a beam of silver atoms in a magnetic field. The absence of the concept of electron spin confused and confounded the interpretation of the SGE, as the silver atoms were, in fact, in a 2S state, with zero orbital and 12 ${{1 \over 2}}$ spin angular momentum. However, a key quantum feature whose existence the SGE was designed to test – namely space quantization of electronic angular momentum – was robust enough to transpire independent of whether the electronic angular momentum was orbital or due to spin. The SGE entails other key aspects of quantum mechanics such as quantum measurement, state preparation, coherence, and entanglement. Confronted with the outcome of the SGE, Stern noted: "I still have objections to the idea of beauty of quantum mechanics. But she is correct." [ABSTRACT FROM AUTHOR]