Issue 6, 2025
Role that hyperfine interaction plays in formation angular distributions of hydrogen-like targets ionization in pump-probe scheme
Role that hyperfine interaction plays in formation angular distributions of hydrogen-like targets ionization in pump-probe scheme
K. A. Gnedovskaya$^1$, M. M. Popova$^{2,3}$, E. V. Gryzlova$^{2,4}$
The article considers depolarization effects, caused by hyperfine interaction of electronic-shell angular momentum and nuclear spin. A pump-probe scheme is analyzed, and the corresponding photo\-electron angular distributions are obtained. Analytical results were illustrated by calculations for a hydrogen-like target. Three most realized polarizations of pump and probe fields are considered: (1) co-linear polarizations, circularly polarized fields with the same (2) and opposite helicity (3).
Show AbstractSoftware implementation of orbit construction methods in the CR3BP
Software implementation of orbit construction methods in the CR3BP
T. A. Syachina, A. G. Rudnitskiy
This paper presents a software implementation of methods for accurate calculation of orbital parameters for near-Earth space, as well as for the vicinity of the Lagrange points. The program is based on modern mathematical models and algorithms providing high accuracy and efficiency of calculations. Various perturbing factors are taken into account and the possibility to model spacecraft motion in complex gravitational conditions is implemented. The results of the program are compared with known software solutions for ballistic and navigation calculations.
Show AbstractFacility for measurement of sky background variations in the infrared at the Caucasian Mountain Observatory of the SAI MSU
Facility for measurement of sky background variations in the infrared at the Caucasian Mountain Observatory of the SAI MSU
I. A. Komarova$^1$, A. M. Tatarnikov$^2$, S. G. Zheltoukhov$^3$
The description of the device constructed at the SAI MSU based on a commercial infrared light-sensitive module for the study of the sky background brightness (SBB) distribution in the infrared is presented. The procedure of observations with the instrument and the algorithm for accounting for the contribution of the instrumental background to the total signal are described. The results of measurements of the SBB at the Caucasus Mountain Observatory at wavelengths of 3.7~$\mu$m and 4.7~$\mu$m carried out in December 2024 are presented. An estimate of the SBB at zenith corresponding to the star $7.3^{\rm m}$ at 1 arcsec$^2$ of the sky is obtained.
Show AbstractAnalysis of hystersis behavior of the lock-in range in a Zeeman ring laser
Analysis of hystersis behavior of the lock-in range in a Zeeman ring laser
E. G. Lariontsev, I. I. Savel'ev$^2$, M. E. Grushin$^2$, E. V. Soukhov$^2$
Broad hystersis area of the lock-in range in a Zeeman ring laser till now were not described theoretically. In this paper we propose a new model accounting an additional coupling of the counterpropagating waves due to their diffraction on the gratings induced in the cavity mirrors. Hysteresis area of the lock-in range have been studied experimentally.
Show AbstractCombining chiral optical Tamm states into one mode of a hybrid structure
Combining chiral optical Tamm states into one mode of a hybrid structure
N. V. Rudakova$^{1,2}$, S. Y. Vetrov$^{1,2}$, I. V. Timofeev$^{1,2}$
The excitation conditions and effective control possibilities are investigated for two coupled chiral optical Tamm states arising at boundaries of a crystalline liquid crystal coupled with polarization-preserving anisotropic mirrors. Numerical modeling has shown that varying the parameters makes it possible to control the magnitude of transmission coefficient of the structure, the optimization of the spectral characteristics, as well as the profile of the local field intensity. In this case, the polarization of the incident light has a significant effect on the excitation efficiency. It is shown that the hybrid mode of two chiral optical Tamm states smoothly transforms into a single Fabry-Perot mode in the process of increasing coupling between them.
Show AbstractIncreasing the efficiency of a laser-plasma source of terahertz radiation using a parabolic concentrator
Increasing the efficiency of a laser-plasma source of terahertz radiation using a parabolic concentrator
A. V. Samsonov$^{1,2,5}$, I. N. Tsymbalov$^{1,3}$, S. A. Shulyapov$^1$, K. A. Ivanov$^{1,4}$, A. B. Savel'ev$^{1,4}$
A 30-fold increase in the energy of a quasi-unipolar terahertz radiation pulse at a remote focus was experimentally demonstrated for the regime of diffuse electron beam generation using a specially designed parabolic concentrator. The coherent terahertz radiation pulse arose due to transition radiation of relativistic electrons accelerated by a femtosecond laser pulse of relativistic intensity (up to 7·10¹⁸ W/cm²) when these electrons exited the plasma layer. The plasma layer was created by exposing an ethanol jet 3 μm thick to a nanosecond laser pulse with an intensity of 10^12 W/cm². Optimization of the plasma layer parameters (maximum electron concentration and thickness) was achieved by varying the delay between the nanosecond and high-power femtosecond laser pulses.
Show AbstractCross-band two-dimentional Fourier spectroscopy technique
Cross-band two-dimentional Fourier spectroscopy technique
G. D. Ivanov$^1$, E. A. Stepanov$^{1,2}$, A. A. Voronin$^{1,2}$, A. S. Shvedov$^1$, A. V. Kargovsky$^1$, A. A. Lanin$^{1,3}$, A. B. Fedotov$^{1,2}$
Two-dimensional Fourier spectroscopy (2D Fourier Transform spectroscopy, 2D FTS) is a non-stationary nonlinear-optical method based on the process of four-wave mixing involving a sequence of three femtosecond pulses. This technique has been widely used to obtain information about the structure and ultra-fast transformation of complex organic and inorganic complexes with characteristic molecular vibrations in the mid-infrared range of two-dimensional Fourier infrared spectroscopy (2D Fourier Infrared Spectroscopy, 2D FTIR). In one of the possible configurations of the 2D FTS technique, excitation and probing of the objects under study are carried out in significantly different spectral ranges. This work demonstrates the experimental implementation of such a cross-range variant of two-dimensional Fourier spectroscopy using the example of recording the vibrational levels of a solution of the organic dye DCM in the frequency range of 1430-1820 cm$^{-1}$ under electronic excitation of the sample by broadband visible-range radiation. It is shown that in a polar solvent, the relaxation of the electronic excitation of the DCM dye is accompanied by the activation of Frank-Condon vibrational modes, which are visible in the two-dimensional Fourier spectrum at frequencies of 1547 and 1576 cm$^{-1}$. We demonstrate that this technique allows for the recovery of the phase of the dye's nonlinear absorption and the resolution of the effects of spontaneous emission and absorption from the excited state. The presented technique of two-dimensional electron-vibrational Fourier spectroscopy can be applied in studies of the photooxidation process of marker proteins, in particular the EGFP protein. Cross-range two-dimensional spectroscopy could be used to study the stress of the protein.
Show AbstractGeneration of vectorial spatiotemporal optical vortices during nonlinear selfaction of an elliptically polarized laser pulse in the isotropic phase of a nematic liquid crystal with a slow nonlinear optical response
Generation of vectorial spatiotemporal optical vortices during nonlinear selfaction of an elliptically polarized laser pulse in the isotropic phase of a nematic liquid crystal with a slow nonlinear optical response
K. S. Grigoriev$^1$, V. A. Makarov$^1$
It has been shown that during the propagation of an initia;;y elliptically polarized light pulse through a nematic liquid crystal in the isotropic phase, at a temperature close to the phase transition temperature, spatio-temporal optical vortices are formed in its circularly polarized components. This occurs due to the large, compared to the pulse duration, temporal inertia of the medium’s nonlinear optical response, which stabilizes the nonlinear collapse.
Show AbstractGeneration of MeV-level multi-charged ions from a relativistic laser-cluster plasma
Generation of MeV-level multi-charged ions from a relativistic laser-cluster plasma
Y. O. Romanovskiy$^{1,2,3}$, A. A. Tausenev$^{1,2}$, T. A. Semenov$^2$, P. A. Shcheglov$^2$, M. V. Chashchin$^2$, A. V. Mitrofanov$^{1,2,3}$, D. A. Sidorov-Biryukov$^{1,2,3}$, M. M. Nazarov$^2$, V. M. Gordienko$^1$
We report a comparative study of MeV-energy multi-charged ion generation efficiency from relativistically intense laser interactions with small and large clusters of atomic Ar and Kr, and molecular O$_2$. An optimal average cluster diameter of 30 nm was identified for krypton to produce ions with MeV energies at ionization multiplicities of 2–5.
Show AbstractMorphological methods for estimating the relative time shift of infrasound signals
Morphological methods for estimating the relative time shift of infrasound signals
A. F. Idrisov$^1$, A. I. Chulichkov$^1$
The present work is devoted to solving the problem of estimating the relative time delay of infrasound signals propagating from a pulse source along different trajectories in a layered homogeneous atmosphere. To solve the problem, morphological methods of signal analysis are used, developed at the Department of Mathematical Modeling and Computer Science, Faculty of Physics, Lomonosov Moscow State University. The methods are applied to the infrasound signals data recorded by barographs located at different points on the Earth’s surface. The time delay of the signals from different barographs allows us to estimate the direction of arrival of the sound wave, which allows us to further determine the position of the signal source and study the structure of the atmosphere.
Show AbstractModeling and processing of correlated measurements in satellite gradiometry
Modeling and processing of correlated measurements in satellite gradiometry
V. E. Zharov$^1$
In this paper, the issue of processing correlated measurements is considered. It is assumed that the true signal is distorted by the device, which, in fact, is a filter with a given amplitude-frequency response. As a result, the signal spectrum changes in the frequency domain, and in the time domain, the value of the measured signal at time $t_i$ depends on the previous values of $t_{i-1}, t_{i-2}, \ldots$. This means that when processing measurements, it is necessary to know and be able to reverse the covariance matrix, which is not diagonal, and may have large sizes. In this case, direct conversion of the matrix is impossible. Therefore, an original method for calculating the inverse covariance matrix and measurement de-correlation is proposed for processing correlated measurements. The developed method is supposed to be used to process the gradiometric data obtained during the GOCE mission and calculation of the spherical harmonic coefficients of the classical series expansion of the Earth’s gravitational field.
Show AbstractFe100-xZrx films (x = 6-13 at. %): relationship between phase-structural state and magnetic parameters
Fe100-xZrx films (x = 6-13 at. %): relationship between phase-structural state and magnetic parameters
D. M. Gridin$^{1,2,3}$, E. V. Harin$^4$, V. A. Tejetov$^4$, G. S. Usmanova$^4$, E. N. Sheftel$^4$, A. B. Granovsky$^{1,5,6}$
The results of measurements of hysteresis loops of Fe100-xZrx films (x = 6-13) are presented both in the initial state after their preparation by ion beam deposition and after annealing in vacuum for 1 hour at 300 and 500 ° C. The measurements were performed on a vibrating magnetometer Lake Shore 7407 in magnetic fields up to 16 kOe at room temperature. An analysis of the data obtained by correlation magnetometry using the model of random magnetic anisotropy has shown that the magnetic properties of films are determined by the coexistence of amorphous and nanocrystalline structures, the volume fractions of which depend on the Zr content and the annealing temperature. For all films, even when the ferromagnetic fraction is several percent, a long-range magnetic order is observed, which is explained by the exchange interaction between neighboring ferromagnetic grains grouped into stochastic domains that are isolated from each other by a paramagnetic amorphous phase. The main magnetic parameters of the microstructure of the films are determined.
Show AbstractMössbauer Study of the Thermally Induced Evolution of the Crystalline and Magnetic Structure of Magnesium Ferrite Nanoparticles
Mössbauer Study of the Thermally Induced Evolution of the Crystalline and Magnetic Structure of Magnesium Ferrite Nanoparticles
T. Yu. Kiseleva$^1$, V. S. Rusakov$^2$, L. A. Lebedev$^3$, Y. A. Khvashevskaya$^4$, V. I. Popkov$^5$
This study presents a Mössbauer spectroscopic investigation of the thermally induced evolution of the crystalline and magnetic structure of magnesium ferrite (MgFe2O4) nanoparticles synthesized via solution combustion, followed by sequential annealing in the 400–800 °C range. The as-prepared product was found to be X-ray amorphous while maintaining a stoichiometric composition, allowing isolated analysis of structure formation during heat treatment. A combination of 57Fe Mössbauer spectroscopy (performed at 300 K and 80 K) and X-ray diffraction was employed to track the crystallization process and magnetic state transitions in the nanoparticle ensembles. Samples annealed at temperatures up to 600 °C exhibit superparamagnetic behavior associated with small crystallite sizes (below ~16 nm). A critical transformation occurs between 600 and 700 °C, where a sharp increase in crystallite size (~24 nm) leads to the emergence of magnetically ordered domains and relaxation-dominated Mössbauer spectra. Further annealing at 800 °C results in structural stabilization and a pronounced reduction in spin relaxation rates, as evidenced by narrowing hyperfine lines and size-related shifts in hyperfine parameters. These findings demonstrate a strong correlation between thermal treatment, structural ordering, and the magnetic response of MgFe2O4 nanoparticles. The study highlights thermal annealing as a key tool for tuning nanoscale magnetic properties through controlled phase development.
Show AbstractCharacteristics of FeSe0.5Te0.5 films on an amorphous substrate
Characteristics of FeSe0.5Te0.5 films on an amorphous substrate
A. V. Petrov$^1$, O. V. Snigirev$^1$, A. G. Maresov$^1$, Yu. V. Blinova$^2$, N. V. Porokhov$^3$, D. A. Chareev$^{4,5}$, A. V. Varlashkin, A. Yu. Tsvetkov
For FeSeTe films on an amorphous dielectric substrate, the surface morphology and elemental composition were investigated. The measured root-mean-square roughness values of the film surface were 4–6 nm in a 1×1 μm² area and 7–10 nm in a 10×10 μm² area. The determined elemental composition, Fe1.05Se0.5Te0.5, was found to be close to the stoichiometric ratio. Estimates of the upper critical fields were obtained: Hc2∥ab(0) ≈ 68 T and Hc2⊥ab(0) ≈ 51 T for different orientations of the magnetic field relative to the crystallographic planes of the film. The corresponding anisotropy value γ of the film properties is about 1.3 and is comparable to the results for such films on single-crystal substrates. The coherence lengths were found to be ξab(0) ≈ 2.5 nm and ξc(0) ≈ 1.9 nm. The critical current density, measured by both contact and contactless methods, was 2.5×10⁴ A/cm² and 6×10⁴ A/cm², respectively, at 2 K. Estimates of the vortex activation energy U(H,T) and the pinning force density were also obtained.
Show AbstractAtomistic modeling of the structure of thin silicon dioxide films using the ReaxFF force field
Atomistic modeling of the structure of thin silicon dioxide films using the ReaxFF force field
F. V. Grigoriev$^1$, S. S. Torbin$^1$, V. G. Zhupanov$^2$, P. A. Novikov$^2$, V. B. Sulimov$^1$, A. V. Tikhonravov$^1$
Molecular dynamics simulation of high-energy deposition of thin silicon dioxide films is performed to investigate their structural features, which are important for modern applications. The structural parameters of the films are calculated. It is revealed that key calculated parameters, such as bond lengths, bond angles, and radial distribution function peak positions, agree well with experimental data. The relative concentrations of point defects, which affect the optical properties of the films, including their radiation resistance, are determined. A two-stage calculation scheme is used: deposition simulation is performed within the DESIL two-particle force field, which allows for the study of films of technologically significant sizes, and their structural parameters are calculated within the more accurate ReaxFF force field. This scheme significantly increased the numerical efficiency of the simulations and yielded new, more accurate data on the concentration of point defects.
Show AbstractMethod for optimizing acceleration structures for applied purposes using genetic algorithms
Method for optimizing acceleration structures for applied purposes using genetic algorithms
M. A. Borisov$^{1,2}$, V. I. Shvedunov$^{1,2}$
The article provide a description of the method of optimizing the structures of linear electron accelerators operating in the standing wave mode based on the genetic method, using the example of optimizing a medical accelerator.
Show AbstractGeneralization and microscopic justification of the material-field form of the Landau-Lifshitz equation for antiferromagnets
Generalization and microscopic justification of the material-field form of the Landau-Lifshitz equation for antiferromagnets
P. A. Andreev$^1$
The derivation of the Landau-Lifshitz equations for antiferromagnets with two types of magnetic ions of different mass is presented. The contribution of the difference in the interaction potentials of different subsystems is discussed (the difference in masses, potentials and magnetic moments corresponds to ferrimagnets). The derivation of the exchange interaction and the contribution of the anisotropy energy is based on the use of the "x, y, z" model. The derivation of the contribution of the Dzyaloshinskii-Moriya interaction is considered. Two modes of the occurrence of the Dzyaloshinskii-Moriya interaction are studied; one is due to the violation of the inversion symmetry in the lattice, and the second is associated with the existence (and displacement) of the ligand ion, which is the oxygen ion. In addition, the possibility of anisotropy of the Dzyaloshinskii-Moriya interaction is taken into account.
Show AbstractPointlike interaction in (2+1)-dimensional spacetime
Pointlike interaction in (2+1)-dimensional spacetime
Yu. V. Grats$^{1,2}$, P. -. Spirin$^{1,2}$
We consider flat three-dimensional spacetime with single extracted point (impurity). For the massless real-valued scalar field on this background, the full set of solutions is constructed. The defect is described within the technique of the Laplacian's self-adjoint extension, where the impurity is identified with the delta-like singularity. It is shown that the appearance of bound states which is undoubtful at a Quantum Mechanics level, corresponds to unphysical states in the Quantum Field Theory. We distinguish physical states and construct exact expression for the renormalized Hadamard function. As an example, the renormalized vacuum field-squared $\langle \phi^{2}(x)\rangle$ is computed to the leading order in the weak-field approximation. It is shown that our toy-model may be considered as a first step to the extended issue of field effects in locally flat conical spaces and in the cosmic-string background.
Show AbstractThe thermal and caloric properties of crystalline argon on the sublimation line
The thermal and caloric properties of crystalline argon on the sublimation line
P. N. Nikolaev
In this work the thermal and caloric properties of crystalline argon at the sublimation line are calculated. A correlation cell-cluster decomposition is used for this. Along the sublimation line, the volume per mole and pressure increase monotonically with increasing temperature. At temperatures below 60K , the pressure becomes 100 times lower than the triple point pressure and then rapidly decreases. The volume per mole remains virtually constant at emperatures below 10K . The heat capacity at constant pressure for the crystalline phase increases monotonically with increasing temperature. A comparison of theoretical and experimental data is performed, and good agreement is found for all regions considered, except for the heat capacity at temperatures below 3K, where collective interactions must be taken into account.
Show AbstractMultielectron ionization of atoms by ion impact in the deposition energy mode
Multielectron ionization of atoms by ion impact in the deposition energy mode
G. I. Andreev, V. L. Bychkov
The PRIMA program has been developed to describe single- and multi-electron ionization of neutral atoms by ion impact. Within the framework of a quasi-classical approach, combining the deposition energy model and statistical probabilities of ionization, the new program allows the calculation of the probabilites and cross-sections of ionization of atoms by ion impact in the energy range from 1 keV до 10 MeV. As an example of the program's operation, calculations of the ionization cross section of neutral xenon by proton impact were performed. A comparison of the ionization cross sections calculated by the PRIMA program with experimental data and calculation results based on the transport equation over a wide range of projectile ion energies showed that the discrepancies do not exceed factor 2-3.
Show AbstractIsomeric ratios in photonuclear reactions for nuclei in the $Z = 60-80$ range
Isomeric ratios in photonuclear reactions for nuclei in the $Z = 60-80$ range
O. V. Poriadina$^1$, S. S. Belyshev$^{1,2}$, A. A. Kuznetsov$^{1,2}$, N. I. Fursova$^{1,2}$, V. V. Khankin$^2$
Photonuclear reactions on a natural mixture of mercury isotopes were studied by the activation method at an electron energy of $E^m$=55 MeV. The reaction yields and isomeric ratios for ${}^{195,197}$Hg and ${}^{198,200}$Au were determined. The obtained results are compared with theoretical predictions from the TALYS 2.0 code. Based on both the present experimental and available literature data, systematics of the isomeric ratios as a function of spin factors were obtained for heavy nuclei in the $Z = 60-80$ range.
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