Bulletin of the Lebedev Physics Institute最新文献

This paper presents a calculation of the sensitivity of the νGeN experiment to the coherent elastic scattering of reactor antineutrinos off germanium nuclei for statistics from the standard operational cycle of a power unit at the Kalinin NPP. The calculation has been performed for several models of antineutrino energy spectra, as well as for different models of germanium response to low-energy recoil nuclei. The results indicate that the uncertainties in the antineutrino energy spectrum and those in the response of the detector material significantly affect the sensitivity.

Using the path integral formalism, quantum-mechanical tunneling is described by instantons—solutions to the equations of system motion in imaginary time. However, in imaginary time, this formalism is suitable only for studying the characteristics of a system in thermodynamic equilibrium and is not applicable to significantly nonequilibrium phenomena. Therefore, it is necessary to develop an approach that takes into account instanton solutions within the framework of the real-time path integral. This paper takes a step in this direction by generalizing the Gutzwiller trace formula, derived within the real-time formalism, for the density of states of a quantum-mechanical system in a tunnel-type potential. It is shown that to obtain real values of the level splitting in a symmetric double-well potential, it is necessary to take into account approximate solutions to the equations of motion in imaginary time, corresponding to multi-instanton configurations.

Differential spectrum of dilepton pair production in a strongly interacting quark plasma (SQP) described within the framework of a formalism of nonextensive/nonadditive statistical physics is considered. A significant growth, increasing with the invariant mass of the pair, in the rate of dilepton pair production as compared to a Boltzmann quark plasma is demonstrated.

We examine the effect of an atmospheric-pressure Ar/CO² microwave torch on nanocarbon films formed on the surface of silicon wafers by vertical deposition from an ethyl colloidal solution of carbon nanoparticles. The spatial distribution of the microwave torch plasma temperature is obtained for the optimal plasma treatment regime, which does not lead to significant morphological changes in the surface. It is shown that the nanocarbon coating exhibits high resistance to plasma loading.

The relative contribution of neutrons to the flux of hadrons with energies ≥20TeV at the level of emulsion chamber (EC) exposures in the stratosphere (~10 g/cm²) is calculated by the Monte Carlo method using the EPOS-LHC model describing high-energy nucleon‒nucleus and nucleus‒nucleus interactions in the CORSIKA-7.7500 software package [1].

We report a possibility of producing silicon particles with Fano resonance by laser ablation in liquid using a nanosecond ytterbium fiber laser with a wavelength of 1060–1070 nm. A silicon wafer with a film of porous silicon doped with boron is used as a target. The results of studying the target and silicon particles with scanning electron microscopy and Raman spectroscopy are presented.

The paper presents curves of potential energy and dipole moments for the X²Π ground state and low-lying A²Σ⁺ and B²Π excited states of the CaO⁺ ion. They were plotted using multiconfiguration methods of electronic structure calculation subject to spin-orbit interaction. Electron-vibrational-rotational spectra caused by spontaneous transitions between vibrational-rotational levels of the X²Π, A²Σ⁺, and B²Π electronic states of the CaO⁺ cation were synthesized on their basis. The calculation results can be used for simulating the optical cooling of the CaO⁺ molecular ion.

This paper presents an integrated study into the acoustic properties of hierarchical 3D-printed metamaterials made of polylactide, which have been developed for utilization in tissue engineering applications. A numerical finite element modeling was carried out to study the propagation of ultrasonic waves in the 1–9 MHz range through lattice structures shaped as octahedrons, honeycombs, or diamonds. The influence of geometric topology and effective physical parameters (Young’s modulus, density, sound velocity) on acoustic pressure distribution is discussed. It is shown that the studied types of triple periodic structures with minimal surface area demonstrate unique patterns for the localization and scattering of ultrasonic field energy. This finding opens up opportunities for using such structures as scaffolds or in controlled drug release with diagnostic function. The findings enable the prediction of the interaction between porous lattice metamaterials and ultrasound and the optimization of their application in dynamics using noninvasive ultrasound diagnostics.

We examine the effect of laser shock peening (LSP) without coating by low-energy (0.3 J) pulses on the structure and residual stresses in a deformed AMg6 aluminum alloy with different crystallographic textures prior to and after recrystallization annealing. It is shown that the initial texture of the alloy dramatically affects the profile and depth of residual stresses after LSP. It is found that the depth and profile of compressive residual stress (CRS) in the aluminum alloy depend on the orientation of the crystallographic planes relative to the applied force. The smallest depth and magnitude of CRS are obtained when the slip plane is located perpendicular to the applied force. With a favorable crystallographic texture, the CRS depth increases by 1.5 to 3 times, depending on the laser power density and spot diameter. It can be argued that the crystallographic texture of the LSP-processed (LSPed) alloy is one of the main factors influencing the results of laser shock peening.

We report experimental data on the UV, visible, and near-IR absorption spectra of a colloid obtained by pulsed laser ablation of gold with Nd:YAG laser radiation in a tetrahydrofuran medium. Data are presented on the dynamics of changes in colloid absorption upon irradiation with unfocused 266 nm radiation, resulting in the formation of a new absorption band peaking at 312 nm.