arXiv subjects

Constantine E. Theodosiou

Publications and source records attributed to Constantine E. Theodosiou.

8 recordsLinked to original sources

arXiv2026

Spin asymmetry for the elastic scattering of polarized electrons from Zn, Cd, and Hg

We present an extensive set of theoretical results for spin asymmetry in the form of Sherman functions for the elastic scattering of electrons by zinc, cadmium, and mercury. This study extends the application of our earlier method of calculations, which we previously employed for stable inert gases and alkaline-earth-metals to these three atoms. Our predictions are in adequate agreement with experimental values and precise theoretical results.

physics.atom-ph↗

arXiv2026

Elastic electron scattering from Zn, Cd, and Hg

We present an extensive set of theoretical results for differential, integrated, and momentum transfer cross sections for the elastic scattering of electrons by zinc, cadmium, and mercury. This study extends the application of our method of calculations, previously employed for stable inert gases and alkaline-earth-metals. Our approach is a self-consistent calculation, with a semi-empirical element in the adjustable cut-off radius of the polarization potential. Our method is expected to provide a set of accurate data for Zn, Cd and Hg, based on the satisfactory agreement in our previous investigations with experimental values and other precise theoretical results.

physics.atom-ph↗

arXiv2024

Elastic electron scattering from Be, Mg, and Ca

We present a comprehensive set of theoretical results for differential, integrated, and momentum transfer cross sections for the elastic scattering of electrons by beryllium, magnesium and calcium, at energies below 1 keV. In addition, we provide Sherman function values for elastic electron scattering from calcium in the same energy range. This study extends the application of our method of calculations, already employed for barium and strontium, to all stable alkaline-earth-metal atoms. Our semi-empirical approach to treating target polarization has produced in our earlier work a satisfactory agreement with experimental values and precise theoretical results such as convergent close-coupling calculations for barium. The present data are expected to be of similar high accuracy, based on our previous success in similar calculations for barium and all inert gases.

physics.atom-ph↗

arXiv2022

Calculation of the near threshold photoabsorption for the ground and excited sodium states

We revisit the photoabsorption from the ground state of Na, ending below and above the ionization threshold, with special emphasis on the shape of the photoionization cross section around the Cooper minimum. The present treatment, using a self-consistent central field and including core polarization effects, matches and improves over the results of other recent calculations. The photoabsorption from the excited $4s,$ $3p$, and $3d$ states is also calculated, along with the corresponding optical oscillator strengths. The results are compared with all published experimental and with the most representative of the theoretical data. The comparisons confirm the results of some of the measurements, but raise serious concerns about the validity of others. The continuing disagreement in the case of the ground state with the only one available experimental measurement, that is over 55 years old, points to the needs for new, refined, measurements.

physics.atom-ph↗

arXiv2022

On the principal series of potassium

We revisit the photoabsorption from the ground state of K through the first ionization limit, and provide recommended values for the optical oscillator strengths. The anomaly in the oscillator strength ratio within each doublet is also revisited and compared with both the experimental data available and the relativistic calculations available.

physics.atom-ph↗

arXiv2022

Calculation of the K $4s, 7s,$ and $4p$ photoabsorption near threshold

We revisit the photoabsorption from the ground state of K, ending below and above the ionization threshold, with special emphasis on the shape of the photoionization cross section around the Cooper minimum. The present treatment, including core polarization effects and dynamic core polarizability matches very well the most accurate measurements resolving an older question about the width of the Cooper minimum. The photoabsorption from the excited $7s$ and $4p$ states is also calculated, along with $4p$$\rightarrow $$nl$ optical oscillator strengths, and compared with recent experimental and theoretical data.

physics.atom-ph↗

arXiv2005

Revisiting the anomalous rf field penetration into a warm plasma

Radio frequency waves do not penetrate into a plasma and are damped within it. The electric field of the wave and plasma current are concentrated near the plasma boundary in a skin layer. Electrons can transport the plasma current away from the skin layer due to their thermal motion. As a result, the width of the skin layer increases when electron temperature effects are taken into account. This phenomenon is called anomalous skin effect. The anomalous penetration of the rf electric field occurs not only for transversely propagating to the plasma boundary wave (inductively coupled plasmas) but also for the wave propagating along the plasma boundary (capacitively coupled plasmas). Such anomalous penetration of the rf field modifies the structure of the capacitive sheath. Recent advances in the nonlinear, nonlocal theory of the capacitive sheath are reported. It is shown that separating the electric field profile into exponential and non-exponential parts yields an efficient qualitative and quantitative description of the anomalous skin effect in both inductively and capacitively coupled plasma.

physics.plasm-ph↗

arXiv2004

Influence of ambipolar potential on the properties of inductively coupled discharges at the bounce resonance condition

The importance of accounting for an ambipolar electrostatic potential or a non-uniform density profile for modelling of inductively coupled discharges is demonstrated. A drastic enhancement is observed of the power transfer into plasma for low-collisional, low-pressure, non-local discharges with non-uniform electron density profiles under the condition of bounce resonance. This enhanced plasma heating is attributed to the increase of the number of resonant electrons, for which the bounce frequency inside the potential well is equal to the rf field frequency.

physics.plasm-ph↗