International Journal of Physics

International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 137–144

DOI: 10.46882/2026/IJP/000206

Research Article

Title: Kinetic Swarm Parameters and Electron Diffusivity Metrics in Non-Equilibrium Nitrous Oxide Discharges

Names of Authors: D. L. Santos¹, A. R. Novak², O. H. Takahashi³

Authors’ Affiliations:
¹ Department of Physics, University of Coimbra, Coimbra, Portugal
² Institute of Plasma Physics, Czech Academy of Sciences, Prague, Czech Republic
³ Department of Physics, Tohoku University, Sendai, Japan

Abstract: Plasma-assisted gas conversion offers a promising technological pathway for carbon capture and the synthesis of green fuels. This study presents a self-consistent kinetic model analyzing electron transport properties and electron-impact dissociation rates in non-equilibrium nitrous oxide (N₂O) plasmas. We solved the electron Boltzmann equation using the two-term approximation across a wide range of reduced electric fields (E/N) from 1.0 Td to 500.0 Td (1.0 Td = 10⁻¹⁷ V-cm²). The cross-section dataset included elastic momentum transfer, rotational, vibrational excitation, dissociative attachment, and direct ionization processes. Our modeling results show that at low reduced electric fields (E/N less than 30.0 Td), over 75.0% of the total electron energy is funneled directly into exciting asymmetric vibrational states. These excited states are essential for driving efficient dissociation via stepwise vibrational ladder climbing. The rate coefficient for dissociative electron attachment peaked at a value of 2.4 x 10⁻¹¹ cm³/s at an E/N value of 85.0 Td. This matches the electron energy threshold where the dissociative cross-section is maximized. We validated our numerical simulations by comparing calculated electron drift velocities and longitudinal diffusion coefficients with independent swarm experimental measurements, achieving an overall variance within ±6.0%. These kinetic coefficients provide essential input data for optimizing industrial gliding arc and dielectric barrier discharge reactors for high-throughput recycling.

Keywords: Gas conversion; Boltzmann equation; Electron transport; Cross-section; Plasma kinetics; Dissociative attachment

Manuscript Timeline: Received: June 18, 2026 / Revised: July 20, 2026 / Accepted: August 05, 2026 / Published: August 28, 2026

Citation: Santos, D. L., Novak, A. R., & Takahashi, O. H. (2026). Kinetic Swarm Parameters and Electron Diffusivity Metrics in Non-Equilibrium Nitrous Oxide Discharges. International Journal of Physics, 17(8), 137–144.

International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 129–136

DOI: 10.46882/2026/IJP/000205

Research Article

Title: Ab Initio Study of Structural Instabilities and High-Pressure Equations of State in Magnesium Silicates

Names of Authors: S. P. Nair¹, J. K. Greenwood²

Authors’ Affiliations:
¹ Department of Physics, University of Kerala, Trivandrum, India
² Department of Earth Sciences, University of Cambridge, Cambridge, UK

Abstract: Investigating the structural behaviour of magnesium compounds under extreme pressures is essential for developing accurate interior models of terrestrial exoplanets and gas giants. We investigated the high-pressure structural phase transitions, elastic constants, and electronic properties of MgSiO³ post-perovskite using ab initio density functional theory within the generalized gradient approximation. The computational model evaluated pressures ranging from 0.0 GPa up to 300.0 GPa. Our total-energy calculations indicate that the system undergoes a structural phase transition to a denser phase at a hydrostatic pressure of 215.0 GPa. This structural transition induces a significant volume collapse of 6.2% at the transition point. We calculated the elastic constants across the entire pressure range to verify mechanical stability. The primary phase meets all Born stability criteria until it approaches the transition pressure, where the shear modulus drops sharply. The electronic density of states revealed that the wide insulator band gap shrinks steadily from 7.80 eV at 0.0 GPa to 5.15 eV at 200.0 GPa. Upon transitioning to the high-pressure phase, the band gap decreases further to 3.90 eV at 300.0 GPa, indicating that the system remains an insulator even under ultra-high core pressures. These precise equations of state provide reliable reference parameters for deep-mantle planetary geophysics.

Keywords: Magnesium silicates; Density functional theory; Phase transition; High pressure; Elastic constants; Equation of state

Manuscript Timeline: Received: June 15, 2026 / Revised: July 18, 2026 / Accepted: August 04, 2026 / Published: August 21, 2026

Citation: Nair, S. P., & Greenwood, J. K. (2026). Ab Initio Study of Structural Instabilities and High-Pressure Equations of State in Magnesium Silicates. International Journal of Physics, 17(8), 129–136.

International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 121–128

DOI: 10.46882/2026/IJP/000204

Research Article

Title: Acoustic Wave Scattering and Waveguide Defect Modes in Elastic Phononic Crystals

Names of Authors: A. M. El-Sayed¹, G. B. Zhou², H. J. Mueller³

Authors’ Affiliations:
¹ Department of Physics, Faculty of Science, Ain Shams University, Cairo, Egypt
² Department of Materials Science, Fudan University, Shanghai, China
³ Institute of Physics, Karlsruher Institut für Technologie, Karlsruhe, Germany

Abstract: Phononic crystals offer exceptional capabilities for manipulating acoustic waves through the formation of complete elastic band gaps. This study examines the propagation of acoustic waves in a two-dimensional phononic crystal consisting of copper cylinders arranged in a square lattice embedded within an epoxy matrix. We performed finite element method (FEM) simulations using the plane wave expansion technique to compute the acoustic band structures. The cylinder radius-to-lattice pitch ratio (r/a) was varied from 0.20 to 0.45 to systematically optimize the system parameters. Our calculations revealed a wide, complete acoustic band gap for both transverse and longitudinal modes within the normalized frequency range of 0.35 to 0.58 when r/a was optimized at 0.42. To validate these numerical simulations, we fabricated a physical prototype containing 10.0 x 10.0 rods positioned within an acrylic frame and filled with liquid epoxy resin. Ultrasonic transmission measurements were performed using water-immersed piezoelectric transducers across a frequency range from 20.0 kHz to 200.0 kHz. The experimental transmission spectra demonstrated a profound acoustic attenuation of up to -45.0 dB within the predicted band gap region, demonstrating excellent agreement with the FEM models. Introducing a line defect into the lattice configuration successfully created an acoustic waveguide channel. This channel demonstrated a high transmission efficiency of 88.0% for localized defect modes, demonstrating the utility of this design for acoustic filtering and noise-isolation.

Keywords: Phononic crystals; Acoustic band gap; Finite element method; Ultrasonic transmission; Waveguide; Elastic waves

Manuscript Timeline: Received: June 12, 2026 / Revised: July 15, 2026 / Accepted: August 03, 2026 / Published: August 21, 2026

Citation: El-Sayed, A. M., Zhou, G. B., & Mueller, H. J. (2026). Acoustic Wave Scattering and Waveguide Defect Modes in Elastic Phononic Crystals. International Journal of Physics, 17(8), 121–128.

International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 113–120

DOI: 10.46882/2026/IJP/000203

Research Article

Title: Quantum Noise Squeezing and Phase Stabilization Metrics in a Triply Resonant Optical Parametric Oscillator

Names of Authors: J. L. Manceau¹, R. T. Howard²

Authors’ Affiliations:
¹ Laboratoire Kastler Brossel, Sorbonne Université, CNRS, Paris, France
² Department of Physics, California Institute of Technology, Pasadena, USA

Abstract: Continuous-wave squeezed states of light are essential resources for quantum metrology, quantum communication protocols, and high-precision gravitational wave detection. This paper describes the design and experimental performance of a triply resonant optical parametric oscillator (OPO). The cavity contains a periodically poled lithium niobate crystal and is driven by a frequency-doubled 532.0 nm laser. By matching the resonance conditions for the pump, signal, and idler fields simultaneously, we achieved an exceptionally low parametric oscillation threshold of only 4.5 mW. We measured the quantum noise levels of the generated sub-harmonic fields at 1064.0 nm using a high-efficiency balanced homodyne detection system. The experimental setup achieved a maximum quadrature noise squeezing level of 8.2 dB below the shot-noise limit at a detection frequency of 5.0 MHz. After accounting for independent detection losses, including a photodiode quantum efficiency of 94.0% and an escape efficiency of 91.5%, the inferred squeezing level at the cavity output was determined to be 11.4 dB. We systematically monitored the stability of this squeezed state over an extended continuous runtime of 4.0 hours. The system maintained a variance of less than ±0.3 dB, enabled by an active digital feedback loop locking the relative phase of the local oscillator. These experimental results show that this OPO configuration provides a stable source of non-classical light for advanced quantum information networks.

Keywords: Quantum optics; Squeezed light; Optical parametric oscillator; Homodyne detection; Quantum metrology; Shot-noise limit

Manuscript Timeline: Received: June 10, 2026 / Revised: July 12, 2026 / Accepted: August 01, 2026 / Published: August 14, 2026

Citation: Manceau, J. L., & Howard, R. T. (2026). Quantum Noise Squeezing and Phase Stabilization Metrics in a Triply Resonant Optical Parametric Oscillator. International Journal of Physics, 17(8), 113–120.

International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 105–112

DOI: 10.46882/2026/IJP/000202

Research Article

Title: Superconducting Critical Fields and Upper Phase Boundaries of Iron-Chalcogenide Single Crystals

Names of Authors: K. A. Tanaka¹, V. N. Volkov², S. C. Williams³

Authors’ Affiliations:
¹ Department of Physics, Tokyo Institute of Technology, Tokyo, Japan
² Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, Russia
³ Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK

Abstract: Iron-based superconductors attract intense interest due to their high critical fields and unconventional pairing mechanisms. We synthesized high-quality single crystals of the iron-chalcogenide superconductor FeSe0.4Te0.6 using a self-flux crystal growth technique. The superconducting properties and phase diagram were investigated via temperature-dependent electrical resistivity and magnetic susceptibility measurements under high DC magnetic fields up to 16.0 T. The pristine single crystals showed a sharp superconducting transition with a critical temperature (Tc) of 14.5 K at zero magnetic field. The transition width was exceptionally narrow at dT = 0.4 K, indicating excellent chemical homogeneity. When an external magnetic field was applied parallel to the crystal ab-plane, the upper critical field, Hc2(0), was estimated to be 48.2 T by applying the Werthamer-Helfand-Hohenberg (WHH) theoretical model. Conversely, with the magnetic field aligned parallel to the c-axis, Hc2(0) dropped to 26.8 T. This response yields an anisotropy factor of approximately Gamma = 1.80 near the transition temperature. The temperature dependence of Hc2 along both crystallographic axes exhibits a distinct linear upward curvature. This behaviour deviates significantly from conventional single-band WHH predictions and strongly implies a multiband superconductivity mechanism. Magnetization loops revealed a high critical current density (Jc) exceeding 2.5 x 10⁵ A/cm² at 4.2 K under zero field. This high current capacity underscores the potential of FeSe0.4Te0.6 single crystals for high-field engineering applications.

Keywords: Iron-based superconductors; Single crystal growth; Upper critical field; Multiband superconductivity; Magnetoresistance; Anisotropy factor

Manuscript Timeline: Received: June 04, 2026 / Revised: July 08, 2026 / Accepted: July 28, 2026 / Published: August 14, 2026

Citation: Tanaka, K. A., Volkov, V. N., & Williams, S. C. (2026). Superconducting Critical Fields and Upper Phase Boundaries of Iron-Chalcogenide Single Crystals. International Journal of Physics, 17(8), 105–112.

International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 97–104

DOI: 10.46882/2026/IJP/000201

Research Article

Title: Plasma Chemistry and E-to-H Mode Transitions in low-Pressure Chlorine Inductively Coupled Discharges

Names of Authors: P. L. Becker¹, M. G. Nielsen², F. E. Silva³

Authors’ Affiliations:
¹ Institute for Plasma Research, University of Stuttgart, Stuttgart, Germany
² Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
³ Department of Applied Physics, University of São Paulo, São Paulo, Brazil

Abstract: Inductively coupled plasma (ICP) sources are widely used in semiconductor manufacturing for precision etching and thin-film deposition. This study characterises the fundamental plasma parameters of a low-pressure chlorine discharge in an ICP system driven at 13.56 MHz. Experimental measurements were collected using a spatially resolvable, compensated Langmuir probe and automated optical emission spectroscopy (OES). We systematically varied the radio-frequency (RF) power from 50.0 W to 600.0 W and maintained the working gas pressure within a range of 0.5 Pa to 10.0 Pa. The Langmuir probe data revealed a distinct transition from the capacitive mode (E-mode) to the inductive mode (H-mode) occurring at an RF threshold power of approximately 180.0 W at 2.0 Pa. In the H-mode, the electron density increased rapidly by over an order of magnitude, shifting from 3.5 x 10⁹ to 5.8 x 10¹⁰ cm⁻³. Concurrently, the electron temperature dropped slightly from 4.8 eV to 3.2 eV due to enhanced electron-neutral collision rates. Spatially resolved profiles demonstrated optimal radial plasma uniformity within ±3.5% across a 200.0 mm diameter substrate holder under a gas pressure of 1.5 Pa. OES line-intensity ratios validated the electron temperature measurements and confirmed a reduction in the plasma sheath potential from 28.0 V to 14.5 V during the E-to-H mode transition. These experimental measurements provide critical validation data for fluid and particle-in-cell simulations of industrial plasma processing systems.

Keywords: Inductively coupled plasma; Langmuir probe; Optical emission spectroscopy; Electron density; E-H transition; Plasma etching

Manuscript Timeline: Received: June 02, 2026 / Revised: July 05, 2026 / Accepted: July 25, 2026 / Published: August 14, 2026

Citation: Becker, P. L., Nielsen, M. G., & Silva, F. E. (2026). Plasma Chemistry and E-to-H Mode Transitions in low-Pressure Chlorine Inductively Coupled Discharges. International Journal of Physics, 17(8), 97–104.