arXiv subjects

M. N. Shneider

Publications and source records attributed to M. N. Shneider.

At least 19 recordsLinked to original sources

arXiv2026

Studies of laser stimulated photodetachment from nanoparticles for particle charge measurements

Determining nanoparticle charge is more challenging than that for microparticles due to change in the particle size during the synthesis substantial plasma property variations, and difficulties in visualizing individual particles, rendering conventional microparticle charge diagnostics ineffective in dusty plasma. In this work, we utilized laser-stimulated photodetachment (LSPD) to deduce the mean charge of nanoparticles. Nanoparticles were grown in an Ar and C2H2 mixture using a capacitively coupled RF discharge and the LSPD induced changes in the electron current monitored by a cylindrical Langmuir probe. LSPD signals were obtained and analyzed across different dust growth phases. The prolonged decay of electron current pulses was attributed to the presence of residual negative ions, caused by the effective electrostatic trapping of these ions and the potential post - LSPD re-formation of new ones. The particle charge was estimated by combining the laser-stimulated photodetachment signal from the probe with the dust density obtained from laser-light extinction using the measured nanoparticle size distribution. For a nanoparticles size range of approximately 100_-_250 nm and mean diameter of Dp ~154.37 nm, the effective mean charge was estimated to be Qd ~37 elementary charge units. The measured charge values are lower than those predicted by orbital motion limited (OML) theory, which may be attributed to significant electron depletion in the nanodusty plasma. LSPD results in Ar and C2H2 nano-dusty plasma confirm the applicability of this method for estimating individual nanoparticle charges. However, it has also been demonstrated that electron detachment from residual background negative ions can influence the detachment current decay and must be carefully considered.

physics.plasm-ph↗

arXiv2025

Thermal Radiation Exchange between Nanoparticles Heated by Arc Discharge

The heating of particles by plasma radiation plays a critical role in space science involving dusty plasma as well as in industrial processes such as plasma vapor deposition, microchip production, etching and plasma fusion. Numerical modeling of radiation heat transfer from plasma to nano-scale particles includes exchange of scattered thermal radiation between particles-an effect that was neglected in prior studies in which temperature of particles was estimated. Thermal modeling of gas loaded with nanoparticles differs from a typical multiphase flow, where particles are assumed to be in thermal equilibrium with the surrounding gas. In contrast, the temperature of nanoparticles heated by radiation is significantly higher than the local gas temperature. The nanoparticles volume heating by radiation is markedly different from conventional surface heating experience by macroscale particles. The larger particles are heated to higher temperatures than smaller ones. The study includes numerical modeling of thermal radiation scattered by particles in the Rayleigh regime in where particles radii are much smaller compared to the radiation wavelength and the distance between particles is larger than the dominant radiation wavelength. The study investigates the effects of reduction in conduction heat flux by reducing the gas pressure and using alternating noble gases. Additionally, it investigates the role of enhancement of radiation heat flux from the arc. The computational results show that the re-radiation by larger, heated nanoparticles is important to obtain the accurate temperature of particles. This inter-particle thermal interaction leads to higher temperatures in smaller particles than models assuming thermally isolated particles would predict.

physics.plasm-ph↗

arXiv2024

Laser-stimulated photodetachment of electrons from the negatively charged dielectric substrates

It is shown experimentally that the photodetachment yield of surplus electrons created by plasma-induced charging of non-conductive surfaces of dielectric materials depends on the initial surface charge density and do not correlate with the tabulated affinity values of these materials. This unexpected result obtained using laser-stimulated photodetachment for fused silica, boron nitride, and alumina, is critically important for the understanding of charging and discharging dynamics, secondary electron emission, and photoemission effects affecting plasma-wall interactions relevant to surface and capacitively coupled discharges, dusty plasmas, electrostatic probe diagnostics and applications for plasma processing of materials, plasma propulsion and gas breakdown.

physics.plasm-ph↗

arXiv2022

A new physical mechanism for the onset of atomic ionization in an optical field with jolts of phase

A theoretical model that describes a new mechanism of atomic and molecular ionization in a low intensity electro-magnetic wave (light or laser beam) with the energy of quanta that is lower than required for a single photon ionization is presented. The essence of the proposed physical mechanism is the step-like gain of energy of a bound electron that occurs every time the phase of the electro-magnetic field jolts. Providing there is sufficiently large number of the phase jolts, the summation of the step increases of the electron oscillation energy can render the total energy of the bound electron such that it exceeds the ionization potential.

physics.atom-ph↗

arXiv2022

Raman mass-spectrometry via oscillatory motion in deep pulsed optical lattices

We describe a new optical diagnostic for determining the composition of gases by measuring the motion of atoms and molecules trapped within very deep optical lattices. This non-resonant method is analogous to conventional Raman scattering, except that the observed spectral features relate to the oscillatory center-of-mass motion of each species within the lattice, determined uniquely by their respective polarizability-to-mass ratio. Depending on the density of the probed sample, detection occurs either via optical scattering at the high end or via non-resonant ionization at the lower end. We show that such a technique is complementary to conventional mass spectrometry techniques and envision its implementation in existing instruments.

physics.optics↗

arXiv2021

Different Perspective on Blue Sky Theory: Theory of Single-Photon Scattering on Bound and Free Electrons

We present a theory of light scattering consistent with modern physics. We proposed a spatial-temporal model of a photon based on classical model of atomic oscillator. Using this photon model, we established a criterion for single vs multi-photon irradiation of matter. We demonstrated that the assumption that induced dipole radiation can be of infinitely small power is inconsistent with quantum mechanics. We proposed the energy criteria for scattering of a photon on single and multiple atoms and free electrons. This criterion revealed the limitations and applicability of Rayleigh's and Thomson's models of scattering. According to our theory, light scattering is a threshold process, and the scattering can only take place for those photons with wavelengths shorter than some threshold. Using our model, we computed the loss of energy by a photon with wavelengths longer than the scattering threshold during interaction with bound and free electrons. We showed that a single photon can lose energy in collisionless interaction with atoms, molecules, and free electrons. The new theoretical model predicts the red shift of photon wavelength resulting from such interactions. In particular, it provides an explanation for the blue color of sky and an alternative explanation for the cosmological red shift.

physics.optics↗

arXiv2019

Predicted response of an atom to a short burst of electro-magnetic radiation

In this work we present a hypothesis that spectral response of atoms or molecules to a pulse of electromagnetic radiation with fast rising or falling fronts would contain a unique emission line that is located approximately near the frequency of the natural oscillations of optical electron. The emission of this "pinging" spectral line would exist during the time that is determined by the time of radiative energy loss by the optical electron. The amplitude of the "pinging" spectral line would be higher for the pulses with faster raising or falling fronts. The simulations using our previously developed model confirmed existence of the "pinging" spectral response. If experimentally confirmed, this work could lead to a new high sensitivity and high signal to noise ratio stand-off detection techniques, a new type of LIDAR, and to other yet unknown applications.

physics.app-ph↗

arXiv2019

Nanoparticles growth in dynamic plasma

Coagulation growth kinetics of nanoparticles in plasma is affected by inter-particle electrostatic forces due to charging phenomenon. In stationary plasmas, unipolar charging of particles results in retardation of particles growth and may result in limitation on a particle size. We demonstrate opposite effect of enhanced particles growth in atmospheric pressure non-stationary arc discharge. Modeling of the nanoparticles growth kinetics revealed the formation of bipolar charge distribution. As a result, reversed (attractive) Coulomb forces promote formation of micrometer size particles in a millisecond time scale as observed in experiment.

physics.plasm-ph↗

arXiv2018

Direct measurement of electron numbers created at infrared laser-induced ionization of various gases

In this work, we present temporally resolved measurements of electron numbers created at photoionization of various gases by femtosecond laser pulse at 800 nm wavelength. The experiments were conducted in $O_2$, $Xe$, $Ar$, $N_2$, $Kr$ and $CO$ at room temperature and atmospheric pressure. Elastic microwave scattering was used to directly measure the electron numbers. Numbers of electrons in the range $3*10^8$ to $3*10^{12}$ electrons were produced by the laser pulse energies 100-700 uJ. After the laser pulse, plasma decayed on the time scale varied from 1 to 40 ns depending on the gas type and governed by two competing processes, namely, the creation of new electrons from ionization of the metastable atoms and loss of the electrons due to dissociative recombination and attachment to oxygen.

physics.plasm-ph↗

arXiv2018

Coagulation model for ion channels in the lipid membranes

A two-dimensional (2D) model is developed to describe the growth of spotty patterns (domains) in the lipid membranes which result from the coagulation of ion channels. It is assumed that the ion channels can coagulate when activated, e.g. the neurotransmitter may act as the surface-active substance for some ion channels in the lipid matrix or the activation may result in increase of polarity of the ion channels that give rise to their coagulation process due to the Brownian diffusive motion. The results show that the domain radius rD of the ion channels scales with time as rD~time^0.4.The slowing and subsequent saturation of the domain radius at longer time periods are in qualitative agreement with experiments.

physics.bio-ph↗

arXiv2018

Self-focusing of CW Laser Beam with Variable Radius in Rubidium Atomic Vapor

Self-focusing of a cw laser beam in rubidium atomic vapor was studied. The beam power and beam spot size at entrance of a glass cell with the rubidium vapor were variable parameters. A steep grow of the threshold power of self-focusing for the small beam radii (< 30 μm) was observed. Our experimental data are in an agreement with the theoretical results published by Semak and Shneider in 2013. Additional experiments in resonance and transparent media are suggested in order to check and extend our measurements.

physics.optics↗

arXiv2017

Plasma Medicine and Osmosis

In this paper, attention is drawn to the importance of accounting for osmotic pressure when analyzing physiological effects on cellular structures in plasma medicine. Interaction of a weakly ionized plasma jet with a saline solution leads to a detectable changes in the saline's ion-molecular composition and hence changes in the osmotic pressure. This, in turn, leads to a stretching or compression of the membrane, depending on the difference of total external and internal pressures. The selective effect of plasma on cells, observed in experiments, is associated with the change in the mechanical properties of membranes (and thereby, a weakening of their protective properties). Corresponding estimates are given in the article.

physics.med-ph↗

arXiv2017

Cavitation near the oscillating piezoelectric plate in water

It is known that gas bubbles on the surface bounding a fluid flow can change the coefficient of friction and affect the parameters of the boundary layer. In this paper, we propose a method that allows us to create, in the near-wall region, a thin layer of liquid filled with bubbles. It will be shown that if there is an oscillating piezoelectric plate on the surface bounding a liquid, then, under certain conditions, cavitation develops in the boundary layer. The relationship between the parameters of cavitation and the characteristics of the piezoelectric plate oscillations is obtained. Possible applications are discussed.

physics.flu-dyn↗

arXiv2017

Counting the electrons in a multiphoton ionization by elastic scattering of microwaves

Laser induced plasmas have found numerous applications including plasma-assisted combustion, combustion diagnostics, laser induced breakdown spectroscopy, light detection and ranging techniques (LIDAR), microwave guiding, reconfigurable plasma antennae etc. Multiphoton ionization (MPI) is a fundamental first step in high-energy laser-matter interaction and is important for understanding of the mechanism of plasma formation. With the discovery of MPI more than 50 years ago, there were numerous attempts to determine basic physical constants of this process in the direct experiments, namely photoionization rates and cross-sections of the MPI, however, no reliable data is available until today and spread in the literature values often reaches 2-3 orders of magnitude. This is due to inability to conduct absolute measurements of plasma electron numbers generated by MPI which leads to uncertainties and, sometimes, contradictions between the MPI cross-section values utilized by different researchers across the field. Here we report first direct measurement of absolute plasma electron numbers generated at MPI of air and subsequently we precisely determine ionization rate and cross-section of eight-photon ionization of oxygen molecule by 800 nm photons $σ_8=(3.32{\pm}0.3)*10^{-130} W^{-8}m^{16}s^{-1}$. Method is based on the absolute measurement of electron number created by MPI using elastic scattering of microwaves off the plasma volume in Rayleigh regime and establishes a general approach to directly measure and tabulate basic constants of the MPI process for various gases and photon energies.

physics.plasm-ph↗

arXiv2017

Charged cell membrane in electrolyte

An effect of membrane surface charge on mechanical properties of the phospholipid bilayer membrane and pores formation is considered. It is shown that the outer and inner surfaces of the phospholipid membrane is always subject to tension, regardless of magnitude and sign of the charges on its surface. This is due to the fact that the Debye length of the extracellular and intracellular electrolyte is always much smaller than the thickness of the membrane, and accordingly the electric field on the outer surface of the membrane is always much larger than the field inside the membrane. This result contradicts the generally accepted notion that a charged phospholipid membrane is similar to a charged capacitor in a dielectric medium and it is always subject to compression. Phospholipid bilayer membrane will be subject to compression only in a very weak electrolyte (~1mM/L), when Debye length is larger than the membrane thickness. It is also shown that the membrane surface charges lead to pore compression when the pore radius is larger than the Debye radius and to the stretching in the opposite case. Difference in the coefficients of surface and edge tension of phospholipid cell membranes can be explained by taking into account the cell membrane surface charge. Simple experiments are proposed to test the influence of the cell membrane surface charge on its mechanical properties.

physics.bio-ph↗

arXiv2017

Invicem Lorentz Oscillator Model (ILOM)

We present detailed theoretical model of electron motion inside of an atom or molecule when subjected to electro-magnetic wave. This theoretical model, that we called Invicem Lorentz Oscillator Model (ILOM), contains Lorentz Oscillator Model (LOM) as a simplified approximation. The ILOM demonstrates artificial nature of the separation of descriptions of electromagnetic wave propagation in media into Linear and Nonlinear Optics.

physics.optics↗

arXiv2016

Bypassing damaged nervous tissue

We show the principal ability of bypassing damaged demyelinated portions of nervous tissue, thereby restoring its normal function for the passage of action potentials. We carry out a theoretical analysis on the basis of the synchronization mechanism of action potential propagation along a bundle of neurons, proposed recently in [1]. And we discuss the feasibility of implement a bypass to restore damaged nervous tissue and creating an artificial neuron network.

physics.bio-ph↗

arXiv2016

Cross-sections for neutral atoms and molecules collisions with charged spherical nanoparticle

The paper presents cross sections for collisions of neutral atoms/molecules with a charged nanoparticle, which is the source of the dipole potential. The accuracy of the orbital limited motion (OLM) approximation is estimated. It is shown that simple analytical formulas for the atoms/molecules and heat fluxes, obtained in the OLM approximation, give an error of not more than 15%, and are applicable in all reasonable range of nanoparticles and weakly ionized plasma parameters.

physics.plasm-ph↗