Ramsauer Effect Research Articles

Theoretical Models of Composite Materials for the Protection Technologies

The work develops the concept of shielding external radiation using composite materials that are a single condensed structure with incorporated specially configured impurities and (or) defects. Using the example of a one-dimensional model of an inhomogeneous power chain, the possibility of the existence of blocking and transparency effects with respect to external radiation, which arise already in the presence of binary impurities, which, in turn, act as the simplest models of composite systems, is shown. It is proposed to use the above property (isomorphic to the experimentally observed Ramsauer-Townsend effect) for the synthesis of composite materials in radiation protection technologies.

Influence of Electron Collisions on Electromagnetic Modes of Plasma Produced by Multi-Photon Ionization of an Inert Gas

Collective electromagnetic modes in weakly ionized plasma formed by multiphoton ionization of inert gas atoms, in which the Ramsauer–Townsend effect takes place, are studied. It is shown that at a relatively low energy of photoelectrons of the order of 1 eV, typical for multiphoton ionization, amplification of electromagnetic waves is possible. Amplification is possible both in the case of rare collisions of photoelectrons with neutral atoms and for collision frequencies higher than electron plasma frequency. At photoelectron energies somewhat higher than 1 eV, aperiodic instability can develop with growth rate whose value is comparable to electron plasma frequency. Detailed analytical and numerical analysis of the effect of collisions of photoelectrons with neutral atoms on the dispersion law of electromagnetic wave and the growth rates of instabilities is presented.

DKP equation in Wigner–Dunkl quantum mechanics framework

This paper explores the topic of relativistic particles with zero spins from a unique perspective. Our approach is derived from the Dunkl derivative, which we used to investigate this issue. By examining the ([Formula: see text])-dimensional DKP equation, we obtain eigenfunctions. Additionally, we replace the standard partial derivative with the Dunkl derivative and solve the relativistic particle problem in a box using the new formalism. We then determine the energy spectrum for this scenario. Following this, we investigate the scattering of the potential step problem and the Ramsauer–Townsend effect separately. Finally, we calculate the coefficients of transmission and reflection.

Revisiting quantum transport across junctions of single and double-Weyl semimetals

Different types of transport in topological semimetals probe the signatures of their band topology directly. Using Landuer-Buttiker formalism, we study transport through a rectangular potential barrier created across a junction between two topological multi-Weyl semimetals (MSMs). In contrast to a regular Weyl semimetal with topological charge J = 1, MSMs are allowed to have monopole charges J > 1. Consequently, the band structures show highly anisotropic dispersions, being linear exclusively in one momentum direction, and exhibiting a power law dependence, governed by the topological charge J, in other two directions. In this work, we restrict ourselves to MSMs with J = 1 and 2, i.e. single- and double-Weyl semimetals, and our study reveals several unconventional features, which are unique to our systems of study and are useful as diagnostic tools for such topological systems and help to understand the role of anisotropies in these systems. Most strikingly, our study uncovers that the barrier becomes completely transparent to the particles obliquely incident on the barrier only when the incident energy (E) exactly equals to the half of the barrier-height (U) with a certain condition. On the other hand, we show that the Klein tunneling, i.e. the perfect transmission of the particles incident normally on the barrier, exists not only in E < U limit but also in E > U limit. Our study also identifies a new limit (E < U) of occurrence of classical Ramsauer-Townsend effect like condition. The results presented in this work could be tested in simple experiments.

Step potential and Ramsauer-Townsend effect in Wigner-Dunkl quantum mechanics

In this paper the continuity equation for Wigner-Dunkl-Schrodinger equation is studied. Some properties of ¨ ν-deformed functions related to Dunkl derivative are also studied. Based on these, the step potential and Ramsauer-Townsend effect are discussed in Wigner-Dunkl quantum mechanics

Diagnosis of inhomogeneous one-dimensional discrete chains by photon scattering

Among the ways to reduce radiation doses (increasing the distance from the source to the person, reducing the time spent in radiation fields, reducing the radiation dose rate of the source) an important role is played by shielding the source of ionizing radiation.Currently, the use of screens is limited by the small selection of materials and the inconvenience of their use, which complicates their operation, installation and replacement, or disassembly.The propagation of a plane wave in a one-dimensional force chain with Hertzian contacts is analyzed in a linear approximation for cases with the presence of incorporated single and double impurities (defects). The algorithm of analytical solution of control equations and finding of reflection and transmission coefficients of incident radiation is determined. In terms of phase shifts, the frequency criterion of multi-modes of generation of transparent modes for inhomogeneous chains (with double impurities) similar to the Ramsauer-Townsend effect in the scattering of electrons by inert gas atoms is established. The obtained theoretical results are consistent with the data obtained from alternative sources. Possibilities of application of terahertz spectroscopy of radiation transmission for structural diagnostics and detection of in homogeneities, impurities and defects in discrete micro-mechanical (granular) systems are discussed. In particular, preliminary experimental data on scattering of terahertz radiation on samples of granular materials with different degrees of packing, from low to densely packed, which clearly indicate the dependence of the transmittance on the degree of packing and the formation of the corresponding band structure of spectra. The obtained results are also discussed in terms of applications to the creation of the element base of photonic circuitry in the sub millimeter range using decorated with impurities and structured low-dimensional discrete power circuits.

Wave manipulation using a bistable chain with reversible impurities

We systematically study linear and nonlinear wave propagation in a chain composed of piecewise-linear bistable springs. Such bistable systems are ideal test beds for supporting nonlinear wave dynamical features including transition and (supersonic) solitary waves. We show that bistable chains can support the propagation of subsonic wave packets which in turn can be trapped by a low-energy phase to induce energy localization. The spatial distribution of these energy foci strongly affects the propagation of linear waves, typically causing scattering, but, in special cases, leading to a reflectionless mode analogous to the Ramsauer-Townsend effect. Furthermore, we show that the propagation of nonlinear waves can spontaneously generate or remove additional foci, which act as effective "impurities." This behavior serves as a new mechanism for reversibly programming the dynamic response of bistable chains.

Time evolution calculation of muon catalysed fusion: Emission of recycling muons from a two-layer hydrogen film

Recycling muon having approximately 10 keV kinetic energy produced in a muon catalysed fusion (μCF) cycle is expected to be a source of negative muon beam with high-spatial/time coherence. We report a time evolution calculation of μCF cycle with a particular focus on the emission of recycling muons from a hydrogen film target. Rate equations for the μCF reactions are solved using the 4th-order Runge-Kutta method. Considering a two-layer solid hydrogen film target composed of 1 mm hydrogen-deuterium layer and 2 µm deuterium-tritium layer, we have numerically simulated the time evolution of the muonic states and their populations in these layers. The muon atomic and molecular processes in the layers are solved simultaneously by introducing a probability of muonic deuterium atoms traveling between the layers via the Ramsauer-Townsend effect. The use of T2 amplifies the recycling muon emission. A weak dependence of the emission fraction of the recycling muons on the T2 concentration is predicted, which can be utilized to minimize the usage of tritium.

Calculation of spin-polarized positronium-helium (2 S3) and electron-helium (2 S3) scattering

Low-energy properties of spin-polarized electron-helium $(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ and spin-polarized positronium-helium $(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ scattering are calculated using the modified confined variational method. To take the van der Waals interaction into consideration, the van der Waals coefficient between positronium and helium $(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ is calculated using the explicitly correlated Gaussian basis. Compared with the ground state noble gases, the larger scattering length and zero pickoff annihilation rate indicates that $\mathrm{He}(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ may be a more suitable cooling gas. In the energy range we considered, no similarity is found for the $S$-wave cross sections between these two scatterings. A Ramsauer-Townsend minimum is observed in spin-polarized electron-helium$(2\phantom{\rule{0.16em}{0ex}}^{3}S)$ scattering due to the large polarization of metastable helium. This may open a new way to find and study the Ramsauer-Townsend effect.

Nonrelativistic effective field theory with a resonance field

We discuss shallow resonances in the nonrelativistic scattering of two particles using an effective field theory (EFT) that includes an auxiliary field with the quantum numbers of the resonance. We construct the manifestly renormalized scattering amplitude up to next-to-leading order in a systematic expansion. For a narrow resonance, the amplitude is perturbative except in the immediate vicinity of the resonance poles. It naturally has a zero in the low-energy region, analogous to the Ramsauer-Townsend effect. For a broad resonance, the leading-order amplitude is nonperturbative almost everywhere in the regime of validity of the EFT. We regain the results of an EFT without the auxiliary field, which is equivalent to the effective-range expansion with large scattering length and effective range. We also consider an additional fine tuning leading to a low-energy amplitude zero even for a broad resonance. We show that in all cases the requirement of renormalizability when the auxiliary field is not a ghost ensures the resonance poles are in the lower half of the complex momentum plane, as expected by other arguments. The systematic character of the EFT expansion is exemplified with a toy model serving as underlying theory.

The Scattering Properties of Gaseous Parahydrogen

In this work, the scattering properties of parahydrogen gas (p-H2) are studied in the temperature-range (1–50) K. These properties are investigated within the framework of the Lippmann–Schwinger formalism for p-H2. This formalism is used to calculate the phase shifts. The calculations are undertaken using Silvera-Goldman potential. The scattering properties of the system—the total, viscosity, and average cross sections—are then computed using these phase shifts. The s-wave scattering length for p-H2 molecules $$a_{o}$$ is determined as $$a_{o}$$ = 7.01 A. The cross sections exhibited the Ramsauer–Townsend effect and resonance peaks. The lifetime of the quasi-bound states for $$\ell - wave$$ $$\left( {\ell = {2,}\,{\text{4, and 6}}} \right)$$ is also computed.

On the Wave Transmission in a Gently Perturbed Weakly Inhomogeneous Non-Linear Force Chain

We have obtained rigorous analytic and numerical solutions of the equations which govern the transport of mechanical perturbations in a gently precompressed 1D Hertz chain. Both finite-length and infinite-length systems have been studied. We examine both discrete and continuousformulations of the mentioned problem. A few families of analytic solutions of the problem given in the form of quasinormal waves and specific resonance modes have been obtained in the linear approximation for weakly perturbed inhomogeneous systems. Resonance modes are proposed to be interpreted as the Ramsauer–Townsend effect which happens due to the inhomogeneity. The obtained analytic results have been compared with numerical solutions of the discrete equations. We observe a multiscaled scenario of the impulse transport in an inhomogeneous force chain which could happens either asymptotically or at the intermittency between discrete- and continuous limits of the formulated problem. The role of a disorder has been also analyzed with the help of the Dyson concept.

Longitudinal electron waves and instability of collisional plasma formed by multiphoton ionization of gas atoms

Longitudinal collective modes in plasma produced by multiphoton ionization of inert gas atoms are studied. The high-frequency and the low-frequency modes in Xe plasma are considered in detail. It is shown that due to the Ramsauer–Townsend effect, photoelectron collisions with neutral atoms lead to a significant increase in decrement of high-frequency mode in the long-wavelength region where this mode frequency is close to the electron Langmuir one. In the region of wave numbers larger than the ratio of electron Langmuir frequency to photoelectrons average velocity, the dispersion law of high-frequency mode is close to the dispersion law of electron acoustic wave, the phase and the group velocities of which are close to photoelectrons' average velocity. In this case, the acoustic wave is weakly damped even for photoelectrons' collision frequencies comparable to electron Langmuir frequency. There is a low-frequency mode along with the high-frequency one. In the region of relatively small wave numbers, this mode describes aperiodic instability with the growth rate not exceeding half of the electron Langmuir frequency. The instability is caused by the Ramsauer–Townsend effect. As the wave number increases, the low-frequency mode transforms into a longitudinal wave, the amplitude of which increases with time. In the region of wave numbers greater than the ratio of photoelectron average velocity to electron Langmuir frequency, the low-frequency wave is strongly damped due to photoelectron collisions. Influence of the spread of photoelectrons in energy on the low-frequency mode is relatively small. In contrast, a finite width of photoelectron distribution over energy leads to significant collisionless damping of high-frequency wave in the short-wavelength region.

High-frequency skin effect in a photoionized inert gas plasma

The penetration of a monochromatic electromagnetic wave into the weakly ionised plasma formed by multiphoton ionization of inert gas atoms has been studied. It is shown how the type of dependence of the photoelectron collision frequency on their velocity determines transverse permettivity in plasma. Explicit expressions for the absorption coefficient in inert gases at different probe radiation frequencies are obtained. In the high-frequency skin effect mode, the possibility of the absorption coefficient increasing due to the Ramsauer-Townsend effect has been demonstrated with argon as an example.

The Hidden Ramsauer-Townsend Effect in Positron Scattering by Rare Gas Atoms

The aim of this work is to present and discuss the Ramsauer-Townsend effect in the context of low-energy positron scattering by rare gas atoms. Opposed to what happens in electron-atom scattering, the competition between the static repulsive and polarization attractive potentials makes the phenomenon improbable in positron case. Nonetheless, we show using a semiempirical potential formulation that, while the effect is explicitly observed in the total cross sections for He and Ne, for the heavier noble gases it becomes “hidden” or implicit. We show that as the atomic polarizability increases, the suppression of s-wave goes to higher energies due to the variation of the scattering length with the polarizability. No specific signature for the effect is found in the shape of the differential cross sections but curiously, while the effect is implicit in the total cross section for Ar, it generates a minimum structure in the momentum transfer cross section. The theme is presented for non-specialist audience with emphasis in basic atomic and scattering theories along with practical results, the main objective being to boost the traditional discussions with a new view on the subject.

Impact of electron collisions on the skin effect in a photoionized inert gas plasma

The interaction of monochromatic electromagnetic radiation with a photoionized plasma formed during multiphoton ionization of inert gas atoms is studied. It is shown how electron collisions with neutral atoms affect the surface impedance and absorption coefficient. The possibility of a significant absorption coefficient growth in the regimes of high-frequency and normal skin effects due to the manifestation of the Ramsauer-Townsend effect was revealed. The conditions under which the interaction of test low-frequency radiation with a photoionized inert gas plasma is similar to the interaction with a dielectric with a permittivity having a small imaginary part are established.

Scattering of exchange spin waves from regions of modulated magnetization

We investigate the reflection coefficient of spin waves propagating in an ultra-thin ferromagnetic film with regions where saturation magnetization is modulated. We find analytically and using micromagnetic simulations that there are transmission resonances that depend on the width of the regions and on the energy of excitation. Our results resemble the quantum-mechanical Ramsauer-Townsend effect in which an electron with certain energies can propagate above a potential field without scattering. Our findings are useful for reconfigurable magnonic devices where the saturation magnetization can be dynamically controlled via a thermal landscape.

The generalized uncertainty principle from the doubly special relativity: Algebraic approach, Ramsauer effect and delta potential

In this paper, we consider the DSR-GUP which was first proposed by two of us [W. S. Chung and H. Hassanabadi, Phys. Lett. B 785, 127 (2018)]. Here, we introduce the deformed derivative corresponding to DSR-GUP to discuss the quantum mechanics based on DSR-GUP in an algebraical way. We use the deformed Fourier transform and its inverse transform to discuss the plane wave in [Formula: see text]-space and Gaussian packet. We also extend our discussion to the (1 + 1)-dimensional case. As examples, we discuss the Ramsauer–Townsend effect and delta potential.

Geometrical optics method in the theory of channeling of high energy particles in crystals

The process of scattering of fast charged particles in thin crystals is considered in the transitional range of thicknesses, between those at which the channeling phenomenon is not developed and those at which it is realized. We demonstrate the possibility of application of the methods of geometrical optics for description of the scattering process. In particular, we study the dependence of the total scattering cross-section of ultrarelativistic positrons on target thickness in this range of crystal thicknesses. In the case of channeling of ultrarelativistic particles we indicate the possibility of the existence of an effect analogical to the Ramsauer-Townsend effect of conversion into zero of the total scattering cross-section at some values of crystal thickness. An important role is noted of the Morse-Maslov index that makes part of the wave function expression in the geometrical optics method.

Quantum mechanics on (anti)-de Sitter background II: Ramsauer–Townsend effect and WKB method

Based on the one-dimensional quantum mechanics on (anti)-de Sitter background [W. S. Chung and H. Hassanabadi, Mod. Phys. Lett. A 32, 26 (2107)], we discuss the Ramsauer–Townsend effect. We also formulate the WKB method for the quantum mechanics on (anti)-de Sitter background to discuss the energy level of the quantum harmonic oscillator and quantum bouncer.