This review discusses the evolution of quantum optical magnetometers intended for biomagnetic measurements, with particular emphasis on magnetoencephalography. The development of modern optically pumped magnetometers has gradually shifted from the pursuit of ultimate magnetic sensitivity toward suitability for dense multichannel arrays. We describe the evolution of nonzero-field all-optical sensors, including single-beam design, operation in the ultra-low-field regime, vector measurements, and fiber-based optical power distribution. Taken together, these developments demonstrate that high-performance biomagnetic sensing can be achieved without RF excitation and with simplified optical layout, making all-optical nonzero-field Bell–Bloom magnetometers a promising platform for distributed neurodiagnostic systems.
Analytical expressions have been derived for the parameters of the spin Hamiltonian of the transferred hyperfine interaction in CaF2:Pu3+. It has been established that the parameter As of the spin Hamiltonian of this interaction is mainly due to charge transfer processes to the excited 5f46d states. The covalency parameters have been estimated using the experimental electron–nuclear double resonance data on CaF2:Pu3+. The splitting of the excited 5fn−16d configurations under the influence of the crystal field has been studied. It has been shown that the splitting of the 6d electron state leads to an increase in the efficiency of the transfer of the hyperfine interaction from the Pu3+ ion to the fluorine nuclei via π bonds and a decrease in the efficiency of the transfer via σ bonds.
MucR is a conserved global regulator in α-proteobacteria, essential for virulence in Brucella and symbiotic adaptation in rhizobia. It primarily acts as a xenogeneic silencer, repressing AT-rich horizontally acquired genes. Structurally, MucR comprises an N-terminal oligomerization domain, a linker region, and a C-terminal zinc finger DNA-binding domain. Here, we report the optimization of NMR experimental condition and NMR resonance assignments for the complex formed by the C-terminal DNA-binding domain of MucR and 3A3T-DNA. Nearly complete assignments are obtained for 1H, 13C, and 15N resonances of the protein and 1H resonances of 3A3T-DNA. Histidine tautomeric state analysis confirms that the two zinc-coordinating histidine residues adopt Nδ1–H tautomeric state. Additional NMR-based analyses provided structural insights into the MucRCTD and DNA complex formation. The NMR assignments provide a good basis for further structural study of the DNA binding and recognition mechanism of MucR.
The results of observation of microwave photoconductivity response induced by spin-dependent recombination effects involving surface paramagnetic centers in silicon wafers are reported. Surface recombination centers were observed in commercially available wafers subjected to oxidization on air at room temperature. The variations of microwave photoconductivity were detected not only under magnetic resonance but also at the magnetic field values corresponding to crossing and anticrossing points of magnetic sublevels of surface recombination centers.
Identifying individual relaxation mechanisms in carbohydrate solutions from single-frequency NMR relaxation-dispersion data often remains ambiguous. Here, we employ a cross-frequency approach combined with variable-temperature multipulse CPMG NMR experiments at 20 and 400 MHz (293–311 K) to deconvolve superimposed pathways of proton transverse relaxation, with the results interpreted using approximation-free kinetic Monte Carlo simulations. For pure water at 20 MHz, the observed dispersion profile is governed predominantly by heteronuclear 1H–17O scalar relaxation of the second kind. In xylose solutions, the dispersion at both frequencies contains an additional dominant contribution from two-site chemical exchange between water protons and saccharide hydroxyl groups. Variable-temperature experiments reveal an inversion of the macroscopic temperature dependence of R2 at the two frequencies: upon cooling, the amplitude of the relaxation-dispersion profile increases at 20 MHz, corresponding to fast-exchange conditions, but decreases at 400 MHz, corresponding to slow-exchange conditions, while the position of the dispersion inflection point remains unchanged at τeff approximately 0.31 ms, consistent with ∆ω−1. Kinetic Monte Carlo simulations reproduce this inversion, show that cooling leads to an exponential increase in the microscopic exchange lifetime τex from about 1.4–4.1 ms, corresponding to an activation energy of about 45 kJ/mol, and yield mutually consistent parameter values at both frequencies. The analysis further gives a chemical-shift difference of about 1.27 ppm between free water and xylose hydroxyl groups, which is independent of concentration.
Extending pulsed-field-gradient (PFG) NMR diffusometry to non-routine nuclei requires distinguishing apparent free-induction decay from the refocusable coherence available during echo-based diffusion experiments. Here, concentrated aqueous AgNO3 is used to evaluate relaxation constraints governing direct-observe 109Ag PFG NMR diffusometry. 109Ag exhibits slow longitudinal relaxation (T1 ≈ 600 s), making experimental throughput a practical limitation, and a short apparent transverse decay (T₂* = 0.1 s), which could suggest restricted diffusion-encoding feasibility. Hahn-echo measurements show that much of this apparent dephasing is refocusable, and Carr-Purcell-Meiboom-Gill measurements quantify the longer refocused transverse relaxation time (T₂, CPMG = 60 s). Using timing parameters selected within these measured relaxation constraints, convection-compensated PFG measurements yielded a 109Ag self-diffusion coefficient of 8.2 × 10⁻10 m2 s⁻1 with a regression-derived relative uncertainty of approximately 2.4
In this study, we performed molecular dynamics simulations of first- and second-generation lysine-based dendrigrafts in aqueous solution over the temperature range from 280 to 340 K. The second-order orientational autocorrelation function and spin–lattice NMR relaxation time are used to describe the orientational mobility of the CH _2 groups in both dendrigrafts. The mobility of the terminal and side CH2-N groups in both macromolecules is in qualitative agreement with the NMR results obtained previously for the lysine dendrimer. The inner groups of the second-generation dendrigraft behave differently from the inner groups in the dendrimer (NMR data) and the ϵ -lysine-based chain. The average backbone end-to-end distance is the same for both dendrigrafts. However, the second-generation dendrigraft exhibits reduced fluctuations in this characteristic. We also showed that the dendrigrafts have a spherical shape. The size, shape, and density distribution of the dendrigrafts are independent of temperature over the studied temperature range. Dendrigrafts are more compact than the lysine-based dendrimer and have a higher density. This leads to some displacement of water and counterions. Consequently, the relative charge of the macromolecule increases, and there are more hydrogen bonds per amino acid residue.
This paper investigates the structural effects of silicon (Si) and boron (B) substitution in AlPO-11 with AEL framework, comparing pure AlPO-11, SAPO-11 (Si-only), and BSAPO-11 (Si + B). Using multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy (1H, 27Al, 29Si, 31P) combined with density functional theory (DFT) calculations (Gauge Including Projector Augmented Waves (GIPAW) method), we demonstrate that Si substitution alone disrupts the ordered AlPO-11 structure, creating five-coordinated Al sites and resulting in heterogeneous Si distribution comprising both isolated sites and larger silica rafts (evidenced by a broad 29Si signal at -110 ppm). In contrast, simultaneous introduction of boron promotes more uniform Si distribution, eliminating silica rafts and reducing silanol groups while increasing medium-strength Brønsted acid sites (1H signal at 3.7 ppm).
Amorphous carbon samples intended for use as effective battery anode materials were studied using solid-state 13C and 1H NMR spectroscopy. The study revealed a number of changes in the amorphous state that occurred during additional processing of the synthesized sample. It was found that sample milling resulted in the appearance of an additional signal in the 13C NMR spectrum with a chemical shift of δ = 110 ppm, attributed to oxides, and an intense proton NMR signal. In the annealed sample, a ratio of sp2- to sp3-hybridized carbon atoms of 21:6 was detected. 1H and 13C NMR studies of the processed samples and modeling showed that thermal annealing at temperatures above 600°C leads to a transition from amorphous carbon to partially ordered graphene-like domains. This structuring is confirmed by the appearance of resonances in the high-field region of the spectrum [δ (1H) = −7.5–7.0 ppm, δ (13C) = −22 ppm], which arise due to increased bulk susceptibility and strong diamagnetic ring currents in limited interlayer spaces ( 8–10 Å). The calculated values of the ring currents correspond to currents induced in π-conjugated fragments consisting of 37–61 hexagonal rings, which provides the first spectroscopic fingerprint of nanoconfined protons in regions of the order of 8–10 Å in the obtained carbon materials.
Nuclear magnetic shielding interaction of backbone nuclei is the most direct probe of secondary structure of proteins due to its wide variation in shielding parameters in response to changes in electronic environments. In this report, we demonstrate the exclusive sensitivity of backbone amide 15N chemical shielding tensor (CST) components to the two adjacent dihedral angles ψ_i-1 and ϕ_i of the amide group using density functional studies of the central alanine residue of a model tripeptide N-formyl–glycyl–alanyl–leucine–amide. Especially, we show that ψ_i-1 has a dominant effect on the 15N principal components σ_11 and σ_22 , whereas ϕ_i affects σ_22 and σ_33 the most. Through the construction of theoretical 15N shielding surfaces of the model tripeptide as functions of ψ_i-1 and ϕ_i , the predicted 15N CSTs are compared with direct 15N shielding calculations for 20 alanine-containing tripeptide segments selected randomly from regular α-helical and β-sheet regions of 13 protein structures available in the literature. In contrast to the poor correlation observed for α-helical segments, β-sheet segments exhibit a significant correlation between shielding-surface-predicted and directly calculated 15N shielding components with σ_22 and σ_iso having the largest correlation, in agreement with experimental 15N chemical shift studies in the literature. Using alanine as a model for other amino acid types, a similar comparison between the alanine-based 15N shielding and the direct 15N CST calculations for 38 tripeptide segments with non-alanine central residues from sheet regions of four proteins reaffirms the unique sensitivity of σ_22 and σ_iso to backbone dihedral angles irrespective of the identity of side chains.
Agate pebble samples were collected at the Tevinskoye deposit (northern Kamchatka Peninsula, Russia). Simple organic radicals trapped in the microcrystalline portions of the sample, consisting predominantly of chalcedony, were studied using EPR spectroscopy. Traces of fossilized carbonaceous matter were discovered in agate for the first time. Due to the free rotation of the radicals in untreated samples, only isotropic EPR spectra associated with ĊH3, R1 ĊH2, R2 ĊH2, and CO2− were observed. The EPR spectra changed upon grinding or heating of the agate samples. The carbon radical Ċ, localized in complex organic molecules, was detected after stepwise annealing of the samples at temperatures above 300 °C. Changes in the g-factor, linewidth, and resonance line shapes of the carbon radical depending on the annealing temperature were investigated and discussed.
This article presents the spatial transport of magnon Bose-Einstein condensate (mBEC) from their excitation region. It is shown that at a magnon density sufficient to BEC formation, a flow of coherent magnons is formed, analogous to the spatial flow of atoms in the BEC state, known as an atomic laser. We successfully reproduced the magnon laser effect, which is largely analogous to an atomic laser. However, unlike an atomic laser, a magnon laser also generates coherent polariton radiation, which we also observed. This new mechanism of coherent radiation and transport opens up new prospects for quantum applications.
A solid product was obtained during a long-term gamma irradiation of liquid hexafluorobenzene in a glass tube under oxygen-free conditions. Complete conversion into a solid was achieved at a total dose of 2.6 107 Gy and there was no significant gas yield. The XPS data show that the product is similar in elemental composition to the parent hexafluorobenzene and the contact angle measurements demonstrate hydrophobicity of the material. Obtained NMR data suggest that the material predominantly consists of perfluoropolystyrene units and short fluoroalkyl fragments present in much smaller amounts.
We describe the principle and applications of the resonant spin inertia technique that is based on optically detected magnetic resonance. It combines optical pumping and Faraday/Kerr rotation probing in a single laser beam and measures spin resonance and the spin inertia effect induced by a modulated radiofrequency field. This method is sensitive, technically simple, and applicable to a wide range of material systems. It provides access to the basic spin properties, including the longitudinal spin relaxation time T_1 , which can be measured selectively for different spin resonances present in the system. We demonstrate the application of the technique to rare-earth Ce ^3+ ions in a YAG matrix, (In,Ga)As/GaAs quantum dots, and lead halide perovskite nanocrystals. The technique allowed to measure T_1 in these systems, ranging from microseconds to milliseconds, and to reveal peculiarities of spin relaxation for charge carriers as well as for spatially indirect excitons.
We study the processes of persistent nondissipative carrier transport in silicon nanostructures containing the dipole boron centers with the negative correlation energy (negative-U). Recording electroluminescence spectra caused by the multiple Andreev reflection (MAR) under the gate voltage conditions stimulating MAR spin-flip transitions between chains of the dipole negative-U boron centers allows to study the stability of nondissipative transport and use MAR to develop new approaches to multimode ODMR measured by the electroluminescence spectra. Spin-dependent transitions of single carriers between chains of the negative-U dipole centers are also revealed by changes in the residual magnetic field because of the Overhauser effect that results from the hyperfine interactions with the 29Si nuclei of the silicon lattice. To achieve this, the electromagnetic induction method is used to study the interrelationship between the influence of the negative-U correlation gap and the residual magnetic field on the MAR characteristics.
This review highlights the research achievements recognized by Zavoisky Award 2023. It summarizes results obtained over the past fifteen years using pulsed electron paramagnetic resonance (EPR) spectroscopy, conducted at the N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry (NIOCh SB RAS) in collaboration with Institute of Russian Academy of Sciences and international partners. A central focus is the development and application of highly stable nitroxide- and triarylmethyl (TAM) radical-based spin labels and probes, synthesized at NIOCH SB RAS, to address a range of fundamental biophysical problems. The last trends in development of pulse dipolar EPR spectroscopy and its application to study biomolecules are also shortly considered.
Spin noise spectroscopy (SNS) has matured from a subtle effect in atomic vapors into a uniquely versatile optical tool for probing spin dynamics in condensed matter. Unlike conventional spectroscopic methods, SNS requires no resonant excitation or optical pumping—it passively probes the stochastic Faraday rotation arising from spontaneous magnetization fluctuations of an equilibrium spin ensemble. This nonperturbative nature, combined with a spin sensitivity that is proportional to the square root of the total probed spins, makes SNS ideal for studying small spin ensembles, local environments, and weakly coupled subsystems. In this review, we illustrate the power of SNS through recent accomplishments. First, we present the balance between nonperturbative measurement and optically induced phenomena, observed in a one-beam stationary experiment. This includes the observation of optically induced effective magnetic field (AC Stark effect) in n-GaAs microcavities, the direct detection of nuclear spin polarization buildup and decay, and the local optical electron to hole recharging of perovskite nanocrystals. Second, we turn to power-independent SNS abilities. We highlight SNS’s remarkable sensitivity to crystalline symmetry—from resolving anisotropic paramagnetic centers in cubic and birefringent crystals to uncovering hidden twinning domains in bulk halide perovskites. Finally, we demonstrate how the optical selectivity of SNS allows one to address individual groups of paramagnetic defects by probe wavelength tuning, a capability unattainable by conventional EPR. These examples establish SNS not only as a powerful diagnostic for fundamental spin physics, but also as a promising tool for future spintronic, magnetometric, and material engineering applications.
A detailed NMR study of translational and reorientation mobility in mixtures of [BMPyrrTFSI] with [LiTFSI] (0; 0.1 and 1.5 mol/kg) was carried out in the temperature range of 278 K ≤ T ≤ 333 K. To realize the NMR advantage, the resonances of the 1H, 13C, 7Li, and 19F nuclei were registered. The diffusion data clearly indicate a strong correlation of the translational motion of all ions in the studied objects at all used temperatures. On the basis of the data obtained, the activation energies, E_a , for translational motion have also been calculated. The energy barriers for the translational diffusion of the IL cations and anions are close, but for the movement of the Li+ cations, the activation energy E_a is significantly greater. It follows that the lithium cation moves together with the solvate shell of a certain number of anions. To investigate the local mobility, the temperature dependences of the spin–lattice relaxation rates in the studied systems were measured. A comparison of the activation energy values calculated from diffusion and NMR-relaxation data indicates that the energy barriers for the translational motion of ions in the system under study are much higher than for local reorientation processes. The data obtained confirm the conclusion that there is a strong solvate shell (big τ_c ) around lithium cations.
This study presents for the first time a comprehensive study of the mechanisms of interaction L-tryptophan (L-Trp) in aqueous solution with platinum (Pt) and gold nanoparticles (Au NPs) of different shapes based on 1H NMR, DOSY spectroscopy, T1 relaxation measurements, and data analysis. This paper introduces criteria for assessing the degree of L-Trp binding to Au NPs, including the probability of π-stacking, such as the multidirectional changes in chemical shift, the slowing of molecular motion, and the contribution of surface-induced relaxation. Based on these criteria, it is shown that the mechanism of interaction between L-Trp and Au NPs is critically dependent on Au NP morphology. The diffusion coefficient data set demonstrates that rod- and star-shaped Au NPs have a significantly stronger effect on translational diffusion than their spherical counterparts, reflecting differences in surface morphology, contact area, and heterogeneity of binding sites (L-Trp: D = (6.50 ± 0.2) × 10⁻10 m2/s, L-Trp + Au RNP: D = (5.50 ± 0.2) × 10 ⁻10 m2/s; L-Trp + Au SNP: D = (5.90 ± 0.20) × 10⁻10 m2/s). The DFT/SAPT analysis complements the experimental 1H NMR data and supplies an independent structural–energetic justification for our interpretation: in the absence of strong shielding by an organic corona, π‑stacking of the indole ring is the most plausible and energetically favorable adsorption mode of L-Trp on Au NPs.
