Electron Collisions Research Articles

Linear and nonlinear resonant properties of electron gas in n-InSb and graphene layers in terahertz range in bias magnetic fields

Abstract The nonlinear conductivity of 2D electron gas in graphene and 3D electron gas in the narrow-gap n-InSb semiconductor has been simulated in terahertz (THz) range by various methods including the direct quantum approach, the quasi-classical kinetics, and the quasi-relativistic hydrodynamics. These methods yield the same results under the electron temperatures ≤100 K when the kinetic electron effective mass used in the nonlinear hydrodynamics is equal to the effective mass in n-InSb and it is equal to some nonzero mass that depends on 2D electron concentration in the graphene. The linear resonant dependencies of the complex electron conductivity are simulated both from the kinetic theory and from the hydrodynamic one. The kinetic dependencies of the resonant conductivity on frequency coincide with ones obtained from the hydrodynamic theory under realistic electron concentrations and collision frequencies. Thus, the nonlinear hydrodynamic equations are valid to describe the nonlinear dynamics of the electron gas in graphene and in n-InSb. The nonlinear hydrodynamics has been applied for simulations of nonlinear propagation of THz electromagnetic waves through the multilayer structures dielectric - graphene or n-InSb - dielectric placed in a bias magnetic field. The simplest three-layer structures demonstrate the sharp nonlinear switching of the transparency of THz waves and the bistability under relatively low values of amplitudes of the incident electromagnetic wave.

Precision spectroscopy of dielectronic recombination experiments for highly charged ions at large facility HIAF: a simulation study

Dielectronic recombination (DR) experiments of highly charged ions not only provide essential atomic benchmark data for astrophysical and fusion plasma research but also serve as a stringent test for strong-field quantum electrodynamics (QED) effects, relativistic effects, and electron correlation effects. High-Intensity Heavy-Ion Accelerator Facility (HIAF), currently under construction at Huizhou, China, has a high-precision spectrometer ring (SRing) equipped with a 450 kV electron-cooler and an 80 kV ultracold electron-target. This advanced setup facilitates precise measurements of the DR process for highly charged ions across a broad range of center-of-mass energies, from meV to tens of keV. In this study, we employ molecular dynamics methods to simulate the electron beam temperature distribution of the ultracold electron-target at the SRing. The simulation results indicate that, following the designed adiabatic magnetic field and acceleration field treatment, the transverse and longitudinal electron beam temperature from the thermionic electron gun can be reduced from 100 meV to below 5 meV and 0.1 meV, respectively. Furthermore, we analyze the impact of this ultracold electron beam temperature on the resonance peaks and energy resolution in DR experiments. The resolution gain at the SRing electron-target is particularly pronounced at small electron-ion collision energies, which provides unique experimental conditions for the DR experiments. Using lithium-like ${ }_{54}^{129} \mathrm{Xe}^{51+}$ and ${ }_{92}^{238} U^{89+}$ ions as examples, we simulate the DR resonance spectrum at the SRing and compare them with the simulated results from the experimental cooler storage ring CSRe. The results reveal that the SRing experiments can resolve fine DR resonance structures with ultra-high energy resolution compared to those from the CSRe. This work lays the foundation for precise DR spectroscopy of highly charged ions at the SRing to stringent test of the strong-field QED effects and extract nuclear structure information.

Experimental and Theoretical Study on Electron Interactions with Acetic Acid Molecules.

The absolute total cross section for electron collisions with acetic acid has been measured using an electrostatic electron spectrometer and linear transmission method for collision energies ranging from 0.4 to 300 eV. Elastic electron scattering from acetic acid within a low-energy range has also been studied theoretically using the Schwinger multichannel and R-matrix methods, in the static-exchange and static-exchange plus polarization levels of approximation for energies up to 15 eV. The absolute total and the integral elastic cross sections display a π* shape resonance at around 1.7 eV and a broad structure spanned between 4 and 10 eV, which can be associated with a superposition of overlapping σ* resonances. We compared the obtained results with data available in the literature regarding the interaction of electrons with acetic acid. The results of electron collisions with acetic acid, methyl formate, and formic acid are also compared and discussed.

Centrality definition in e + A collisions at the electron–ion collider

Abstract In this work, we investigate the feasibility of defining centrality in electron-ion collisions at the Electron-Ion Collider (EIC) by examining the correlation between the impact parameter and several observables, including total energy, total transverse momentum, and total number of particles. Using the BeAGLE Monte Carlo generator, we simulate e+Au and e+Ru collisions at different energies and analyze the correlation between the impact parameter and these observables across different kinematic regions. Our findings indicate that the correlation is weak in the central rapidity region but becomes stronger in the forward and far-forward rapidity regions. However, the correlation is not sufficiently robust to allow for precise centrality determination. We conclude that defining centrality in electron-ion collisions is more challenging than in ion-ion collisions, necessitating further studies to develop a robust centrality definition for the EIC.

Monte Carlo Modeling and Simulation of Electron Dynamics in Low Temperature Methane Gas

This study examines the collisions of electrons with methane molecules to determine the cross-sections required for calculating electron transport coefficients in methane gas. Employing Monte Carlo Simulations in MATLAB, critical transport characteristics, including electron mobility and diffusion coefficients, were computed. These simulated coefficients are subsequently compared to experimental data to validate the accuracy of the current study’s findings. This comprehensive approach ensures the precision of the performed calculations and their alignment with empirical evidence, thereby enhancing the understanding of the complex interactions and dynamics between electrons and methane molecules in this system.

Origin of the strong anharmonic-induced abnormal thermal conductivity in semiconductors

Abstract Semiconducting materials are the foundations of electronics and optoelectronics, and their heat management guides the design of highly efficient devices. For most semiconductors, the thermal conductivity of materials composed of light chemical species is higher than that of the iso-structured materials with heavy elements. For example, bulk Si shows a thermal conductivity higher than Ge. However, for many copper-based compounds, e.g. Cu halides, the thermal conductivity increases monotonously as the atomic number of halogens increases. On the other hand, for lead chalcogenides, the thermal conductivity of PbSe is lower than PbS and PbTe. In this work, we reveal that the combined effect of electronic states coupling and phonon collisions, giving rise to strong anharmonicity, is responsible for the abnormal trend of thermal conductivity of Cu halides and Pb chalcogenides. From CuCl to CuBr and CuI, the increasing thermal conductivity is due to the decreasing electronic coupling strength between Cu-occupied 3d and unoccupied 4s states when crystal symmetry is reduced, which leads to the increase of atomic vibrational potential energy and reduction of lattice anharmonicity. In Pb chalcogenides, the unusually lower thermal conductivity of PbSe than PbTe and PbS is mainly due to the intensive scattering between phonons caused by the localized transverse acoustic modes and soft optical modes, which outweigh the contribution of the crystal anharmonicity due to the anharmonic potential energy surface.

Study of the structure of atomics by the method of electron scattering in the distorted-wave approximation: Atomic energy

Using distorted-wave approximation obtained the differential cross-section (DCS) of elastic scattering at energy of 80 eV of electrons on 49In, 31Ga, 34Se and 70Yb atoms, and calculated accordingly on the proposed mathematical method. The electron density distribution in the atom is chosen as a function calculated in the Dirac-Hartree-Fock-Slater approximation, which is a superposition of the spherically symmetric Yukawa potential. In addition, the DCSs were calculated for the electron density in the 49 In and 20 Ca atoms expressed as a three-parameter Fermi function at incident electron energy of 100 eV. The obtained theoretical calculations of the cross sections were compared with the experimental data. Besides, the proposed mathematical method simplifies the calculation of integral expressions and makes it possible to obtain a convenient and simple expression for the atomic form factor. Data on the scattering cross sections of electrons on atoms are of considerable interest both in the field of fundamental science for in-depth study of interaction processes and in practical applications, and are necessary in many areas of research, such as modeling low-temperature plasma, astrophysics phenomena, laser physics, and atmospheric effects etc. In addition to natural phenomena, the processes of collision of electrons with matter play an essential role in plasma technologies, such as, for example, microelectronics and biomedicine. Atomic physics, plasma physics and optics - fields directly related to electron-atom make a significant contribution to the fundamental understanding of the world. Despite the long study of the effects of electron scattering on atoms, and the results obtained in the physics of atomic collisions, this area still requires theoretical and experimental research, there is a significant lack of data on collision cross sections for their subsequent use in modeling and calculations. In particular, there are no systematized data on the cross sections for elastic scattering of high energy electrons by atomic.

Direct quarkonium production in DIS from a joint CGC and NRQCD framework

We compute the differential cross section for direct quarkonium production in high-energy electron-nucleus collisions at small x. Our computation is performed within the nonrelativistic QCD factorization formalism that separates the calculation into short distance coefficients and long distance matrix elements that depend on the color and spin of the state. We obtain the short distance coefficients of the production of the heavy quark pair within the framework of the color glass condensate effective field theory, which resums coherent multiple interactions of the heavy quark pair with the nucleus to all orders. Our results are expressed as the convolution of perturbatively calculable functions with multipoint lightlike Wilson line correlators. In the correlation limit, we establish the correspondence between our color glass condensate formulation with calculations employing the transverse momentum dependent (TMD) framework. We extend this correspondence by resumming kinematic power corrections within the improved TMD framework, which interpolates between the TMD formalism and k⊥-factorization formalism. We present a detailed numerical analysis, focusing on J/ψ production in the kinematics accessible at the future Electron-Ion Collider, highlighting the importance of genuine higher-order saturation contributions when the electron collides with a large nucleus. Our results are also valid in the photoproduction limit where we expect the largest contribution from genuine higher-order saturation contributions which could be accessed in ultraperipheral collisions of relativistic heavy ions. Published by the American Physical Society 2024

Flow of viscous electron fluids over sphere

The transport of strongly interacting electrons in ultrapure crystals is usually considered as the movement of an electron fluid. The study of various physical phenomena associated with the flow of electrons in superconducting materials in many problems can be realized from the point of view of the movement of viscous fluids. The article presents an analytical solution to the problem of electron fluid flowing around a spherical obstacle in the case when electrons strongly interact with each other. Expressions for the profiles of the longitudinal and transverse velocity components were obtained for the first time. The influence of electron collision effects and slip effects on the vibrational characteristics of velocity profiles is analyzed. The impossibility of flow separation and the formation of a Karman vortex street in an e-fluid are shown.

Effect of attack angle on the electromagnetic wave transmission characteristics in the hypersonic plasma sheath of a re-entry vehicle

The attack angle may greatly affect the hypersonic plasma sheaths around the re-entry vehicle, thereby affecting the transmission characteristics of electromagnetic (EM) waves in the sheaths. In this paper, we propose an integrated three-dimensional (3D) model with various attack angles and realistic flying conditions of radio attenuation measurement C-II (RAM C-II) re-entry tasks for analyzing the effect of the attack angle on the transmission characteristics of EM waves in the sheaths. It is shown that the electron density and collision frequency of the sheath on the windward side can be increased by an order of magnitude with the increase of the attack angle. Meanwhile, the thickness of the sheath on the leeward side is increased where the electron density and collision frequency are reduced. The EM waves are mainly reflected on the windward plasma sheath due to the cutoff effect, and the radio-frequency (RF) blackout is mitigated if the antenna is positioned on the leeward side. Thus, by planning the trajectory properly and installing the antenna accordingly during the re-entry, it is possible to provide an approach for mitigation of the RF blackout problem to an extent.

A comparison of the acoustic waves generated in proton and carbon ion therapy

Hadron therapy, which employs particles such as protons and carbon-ions, is a promising method of cancer treatment due to its unique ability to deliver maximum energy at the Bragg peak near the tumor, sparing surrounding healthy tissue. Ionoacoustic waves, generated by thermal expansion from electronic collisions and localized heating, can be detected to optimize dose delivery and verify particle range, thus improving treatment precision. These waves offer a unique opportunity for comparative studies of different particle therapies. In this study, a mathematical model and computational simulations are used to compare the characteristics of ionoacoustic waves generated in tissue by proton and carbon-ion beams. In particular, we assess the impact of the nuclear fragmentation tail on the ionoacoustic signals generated in carbon-ion therapy. Our approach will allow us to make some important observations to study the comparative effects of proton and carbon-ion therapy. The aim of this work is to perform a comprehensive comparative analysis of ionoacoustic waves from proton and carbon-ion treatments, focusing on their potential for in-vivo range verification. This research addresses the current gap in understanding the use of ionoacoustic signals for range verification in ion beam therapy, which is critical given the growing clinical application of carbon ion therapy and its under-explored acoustic properties. This study pioneers the feasibility of using acoustic imaging from carbon-ion beams to detect the Bragg peak position and measure tumor dose in real-time. Carbon-ion dose mapping and relative biological effectiveness (RBE) assessment can be facilitated by real-time signal monitoring. Our study aims to significantly advance the field by addressing the lack of a verification technique for carbon-ion beams, focusing on the considerable impact of the nuclear fragmentation tail on ionoacoustic signal waveforms, which provides crucial insights into the unique energy deposition properties of carbon-ions.

Influence of the ionic electric field on Stark shifts of neutral helium lines in plasmas

In this work we provide a contribution to Stark shift for some lines of neutral helium in plasmas. The mentioned shift is caused by the collisions of the unbounded electrons with helium atoms in plasmas. We calculate this contribution by taking into account only weak collisions. This contribution takes into consideration the presence of the local electric microfield created by the ions that constitute in part the plasma. The effect of this microfield modifies the electron trajectory and therefore changes the shift formula developed early by using the straight trajectories in the case of neutral emitters. Our new contribution to the Stark shift caused by electron's collision is applied to some HeI lines: 3188 , 3888 , 6678 and 7065 . Our results are confronted with the experimental and theoretical data from the literature which clearly show that the influence of the local electric microfield created by the ions on the Stark shift caused by electron's collision is not negligible and must be taken into account. It turns out that the correction to the theoretical shift for the lines under consideration tends to red.

Spatial imaging of polarized deuterons at the Electron-Ion Collider

We study diffractive vector meson production at small-x in the collision of electrons and polarized deuterons e+d↑. We consider the polarization dependence of the nuclear wave function of the deuteron, which results in an azimuthal angular dependence of the produced vector meson when the deuteron is transversely polarized. The Fourier coefficients extracted from the azimuthal angular dependence of the vector meson differential cross-section exhibit notable differences between longitudinally and transversely polarized deuterons. The angular dependence of the extracted effective deuteron radius provides direct insight into the structure of the polarized deuteron wave function. Furthermore, we observe slightly increased gluon saturation effects when the deuteron is longitudinally polarized compared to the transversely polarized case. The small-x observables studied in this work will be accessible at the future Electron-Ion Collider.

Breit interaction in dielectronic recombination of hydrogenlike xenon ions: storage-ring experiment and theory

Electron-ion collision spectroscopy of the KLL dielectronic recombination (DR) resonances of hydrogenlike xenon ions was performed at a heavy-ion storage ring with a resolving power that is competitive with x-ray spectroscopy of inner-shell transitions in highly charged ions. The KL1/2L1/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$KL_{1/2}L_{1/2}$$\\end{document}, KL1/2L3/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$KL_{1/2}L_{3/2}$$\\end{document}, and KL3/2L3/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$KL_{3/2}L_{3/2}$$\\end{document} resonance groups and even parts of their fine structure are individually resolved. The resonance strengths were measured on an absolute scale and compared with results from multi-configuration Dirac–Fock (MCDF) calculations. These are in excellent agreement with the experimental findings when QED effects on the resonance energies and the Breit interaction are considered. As already found for DR of hydrogenlike uranium (Bernhardt et al. in Phys Rev A 83:020701(R), 2011), this interaction is particularly strong for the KL1/2L1/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$KL_{1/2}L_{1/2}$$\\end{document} resonance group. For U91+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{91+}$$\\end{document}, it increases the KL1/2L1/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$KL_{1/2}L_{1/2}$$\\end{document} DR resonance strength by 40%. For Xe53+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{53+}$$\\end{document}, the increase is found to amount to 25%, confirming the prediction that the influence of the Breit interaction grows with increasing nuclear charge. A comprehensive appendix treats the derivation of experimental and theoretical merged-beams recombination rate coefficients for interacting beams of relativistic electrons and ions.Graphical abstract

A global model and two-dimensional simulation study of a low-pressure inductively coupled CF4 plasma considering non-Maxwellian EEDF

We analyze the discharge characteristics of a low-pressure inductively coupled CF4 plasma using a global model and a two-dimensional (2D) simulation. We first conducted a study comparing the experimental results with the global model, which makes it easier to compare the trend concerning external parameters and less computationally expensive, to validate the chemical reaction data, and then, compared the experimental results with the 2D simulation results. We then analyzed the discharge characteristics by comparing the 2D model results with the global model at various gas pressures and powers. The simulations were performed using COMSOL software, which is based on a fluid model. The electron energy distribution function (EEDF) was solved self-consistently using the Boltzmann equation solver, and then, coupled with the fluid model. The results were more consistent with the experimental results when the EEDF was calculated by solving the Boltzmann equation than for assuming the Maxwellian EEDF. Furthermore, the global model results were similar with the mean values obtained from the 2D model. This indicates that it is efficient to first validate the electron collision cross sections and reaction coefficients using the global model. Our approach is expected to be utilized in the analysis of new gases.

Atmospheric pressure plasma jet interacting with a droplet on dielectric surface

Abstract The chemical processes at plasma–liquid interface has become a crucial point for plasmas’ various applications. In this study, the interaction between atmospheric pressure plasma jet and different-scale droplets were investigated by both experiments and modeling. The interaction transited from ‘annular’ mode to ‘solid’ mode when plasma involved with different size of droplets. As the droplet size increased, the high-field region moved from the plasma jet head to the gap between plasma jet head and droplet vertex surface. Additionally, the time averaged surface fluxes of the main active species were analyzed. For the flux of singlet oxygen (1O2), both small and medium-scale droplets reached the maximum value in the central region of the droplets, while for large-scale droplet, the maximum value was observed in the edge region of the droplet. This was due to the fact that, compared to small and medium-scale droplet, the edges of large-scale droplet are closer to the He–Air mixed boundary layer, where more oxygen molecules were provided in the gas environment, leading to enhanced electron collision reactions with oxygen molecules. The cause for these behaviors were also analyzed and discussed. This work shed light on the interaction mechanism for plasma–liquid interactions, which provides significant guidance for plasma medical or water treatment applications.

What does it take to stabilize a naphthalene anion?

We investigate attachment of slow electrons (0-10eV) to naphthalene (Np) clusters in a crossed beam experiment. Supersonic expansions under different conditions using different buffer gases generate the clusters: in He, Ne, and low pressure Ar, neat (Np)N clusters are formed, while we also observe mixed clusters of naphthalene with rare-gas atoms in co-expansion with Ar above 0.5bar and with Kr. Negatively charged (Np)n- and Rgm(Np)n- (Rg = Ar, Kr) clusters are analyzed by mass spectrometry, and electron energy dependent ion yields are measured. We show that the smallest stable naphthalene complex with an excess electron, the dimer (Np)2- anion, cannot be formed in a binary collision of a free electron with (Np)2 dimer, nor with (Np)3 trimer. Evaporation of a weakly bound Ar atom(s) from a mixed ArM(Np)2 cluster following electron attachment leads to the dimer (Np)2- anion. Larger (Np)n-, n > 3, transient cluster anions decay via evaporation of an Np unit on a timescale of tens of microseconds. The self-scavenging process opens around 6eV, where a naphthalene unit is electronically excited by the incoming electron, which is slowed down and trapped. However, the transient negative ion is efficiently stabilized only in the mixed clusters, from which Ar atom(s) can be evaporated.

Coherent photo- and electroproduction of charmonia on nuclear targets revisited: Green function formalism

We study for the first time the production of charmonia in nuclear ultraperipheral and electron-ion collisions based on a rigorous Green function formalism. Such formalism allows to incorporate properly formation effects (color transparency), as well as the quantum coherence inherent in higher-twist shadowing corrections related to the |QQ¯⟩ Fock component of the photon. The leading twist gluon shadowing associated with multigluon photon fluctuations is also included within the same formalism. The later effect represents the dominant source of shadowing at midrapidities in the LHC kinematic region, while the reduced effect of quark shadowing leads to a significant modification of differential cross sections dσ/dy at forward and/or backwards rapidities. Model calculations for dσ/dy are in a good agreement with available ultraperipheral nuclear Pb−Pb collisions data on coherent charmonium production at RHIC and the LHC. In addition, we also perform predictions for nuclear effects in the electroproduction of charmonia, which can be verified by new data from electron-ion colliders. Published by the American Physical Society 2024

Simulation on the hollow cathode discharge in hydrogen

A rectangular hollow cathode discharge (HCD) in hydrogen with a pressure of 2 Torr is simulated using a 2-D fluid model. The potential, electric field, particle density, and average electron temperature are calculated. The discharge space consists of the cathode sheath region near the cathode electrode and the negative glow (NG) region in the central region of the discharge cell. A high electric field of thousands of V/cm and a low electric field of tens of V/cm appear in the cathode sheath region and NG region, respectively. The average electron temperature in the cathode sheath region is tens of eV, which is significantly higher than that in the NG region. Electrons and H3 + are the main negative particles and positive ions, whose peaks appear in the NG region, and the peak magnitude is on the order of 1010 cm−3. H atom is the highest-density neutral particle other than H2 with a peak density of 1013 cm−3. The reaction kinetics of the generation and consumption of different particles are explored. The results show that each reaction generates certain particles while consuming other particles, ultimately achieving a dynamic equilibrium in the density of various particles. The electrons mainly originate from the ground state ionization between electron and H2 (e+H2 → e+H2 ++e) and are consumed by the dissociative attachment (e+H2 → H−+H). The charge transfer collision reaction (H2 ++H2 → H3 ++H) is the only reaction that produces H3 + ions. Different reactions to the consumption of H3 + ions do not differ significantly. The generation and consumption of H mainly originate from the electron collision dissociation reaction (e+H2 → e+H+H) and the ionization reaction (e+H→H++2e).

Non-Oxidative Coupling of Methane via Plasma-Catalysis Over M/γ-Al2O3 Catalysts (M = Ni, Fe, Rh, Pt and Pd): Impact of Active Metal and Noble Gas Co-Feeding

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al2O3 are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C2+ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:{\ ext{m}\ ext{o}\ ext{l}}_{\ ext{C}{\ ext{H}}_{4}}^{-1}$$\\end{document} and from 9 to 4.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:\ ext{m}\ ext{o}{\ ext{l}}_{{\ ext{C}}_{2+}}^{-1}$$\\end{document}. Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.