The European Physical Journal D最新文献

Quantum information-theoretical measure in terms of Shannon and Fisher entropy in conjugate position and momentum spaces provides important information about the localization/delocalization patterns of the inter-atomic charge density under arbitrary confining environments. In this article, we have attempted to employ such measures to the ground, excited, and the virtual states arising out of two-photon transitions ((1srightarrow nl); (n=2-4), (l=0,2)) of weakly coupled classical plasma embedded H iso-electronic ions (nuclear charge, (Z = 2 - 5)). The wavefunction for the said states is essentially a linear combination of the Slater-type orbitals, the coefficients of which are generated from a fourth-order time-dependent perturbation theory within the variational framework. A complementary nature has been noted in the Shannon and Fisher measures versus the plasma screening parameter plot in the conjugate spaces. A novel scaling law has been proposed to replicate the variation of the Shannon and Fisher entropy w.r.t. Z for the virtual as well as real 2p states of free and plasma confined ions.

We have analytically determined the refractive index for the mechanical refraction of a relativistic particle for its all possible speeds. We have critically analysed the importance of Descartes’ metaphysical theory and extended it in this regard. We have considered the conservation of the tangential component of the relativistic momentum and the relativistic energy of the particle in the process of the mechanical refraction within the optical-mechanical analogy. Our result for the mechanical refractive index exactly matches with the forms of both the Fermat’s result on Snell’s law of optical refraction at the ultra-relativistic limit and the Descartes’ metaphysical result on the pseudo-Snell law of optical refraction at the non-relativistic limit.

Mechanical refraction from medium-1 to medium-2 for (U2>U1)

The hydrogen molecular ion, (H_2^+), is considered in the fixed nuclei approximation. The oscillator strengths relevant to free-bound transitions in (H_2^+) are presented as asymptotic expansions in an inverse power of the internuclear separation, which is assumed to be large. The asymptotic technique leads to an algebraic representation of the oscillator strengths, contrasting with numerical tables.

Recently, convergent close-coupling calculations have been completed for positron scattering from the carbon and oxygen atomic targets. These, together with previously completed calculations for atomic hydrogen, are utilized to perform positron scattering calculations for molecular hydrogen ((hbox {H}_2)), molecular oxygen ((hbox {O}_2)), diatomic carbon ((hbox {C}_2)), carbon monoxide (CO), carbon dioxide ((hbox {CO}_2)), ozone ((hbox {O}_3)), water ((hbox {H}_2hbox {O})), and methane ((hbox {CH}_4)) through a modified independent atom approach. For these molecules, positronium-formation, direct ionization, electron-loss, elastic, total electronic excitation, total inelastic, and total cross sections are obtained for energies between 0.1 and 5000 eV. There is, in general, good agreement between the current results and past experiments for most transitions, particularly at high energies where this approach is expected to be most accurate.

The ionising interactions of high-energy particles with molecules have applications in many areas. Despite this, some areas, including positron scattering, lack experimental data due to difficulties in performing experiments. Here, quick and simple methods for computing direct electron and positron impact ionisation cross sections are presented. These calculations, performed using the open-source software RAPID-CS, can provide a complete data set as a first approximation for when experimental, or more detailed computational work is not available. The cross-sectional data set includes the total, partial/fragment-specific, single-differential, average secondary electron energy and stopping power cross sections. The molecules N(_2), O(_2) and CO were chosen to study due to the availability of positron scattering data. An overall good agreement with experimental and other computational results is presented.

Direct electron (left) and positron right) impact partial ionisation cross sections for N2. Total cross section: red, (N^{+}_{2}) partial cross section: blue, N(^{+}) partial cross section: green.electron: solid lines: BEB, experimental measurements by Lindsay and Mangan [36]:Ürosses, Straub et al. [37]: stars, Opel et al. [39]: squares. Positron: solid lines: BEB0, Dashed lines: BEBA, Marler and Surko [23]: red crosses, Bluhme et al. [24]: stars

A magnetically tunable multi-band switchable frequency terahertz (THz) absorber based on graphene is proposed, and its absorption performance is analyzed using the (4 times 4) transfer matrix method. The results indicate that the proposed absorber achieves absorption amplitude tuning across multiple switchable THz frequencies by adjusting the static bias magnetic field. Moreover, both absorption and modulation depths exceed 90% for the left-handed circularly polarized wave. This performance can be attributed to the unequal Landau levels distribution of graphene in the quantum domain and the properties of photonic crystals, which include photonic bandgaps and optical localization. This study may have significant potential in various frequency-switchable components, such as circular polarization sensors, circular polarizers, and magnetic circular dichroism optical detectors.

The paper studies resonant generation of higher-order harmonics in a closed cavity in Euler-Heisenberg electrodynamics from the point of view of pure quantum field theory. We consider quantum states of the electromagnetic field in a rectangular cavity with conducting boundary conditions and calculate the cross section for the merging of three quanta of cavity modes into a single one ((3 rightarrow 1) process) as well as the scattering of two cavity mode quanta ((2 rightarrow 2) process). We show that the amplitude of the merging process vanishes for a cavity with an arbitrary aspect ratio and provide an explanation based on plane wave decomposition for cavity modes. Contrary, the scattering amplitude is nonzero for specific cavity aspect ratio. This (2 rightarrow 2) scattering is a crucial elementary process for the generation of a quantum of a high-order harmonics with frequency (2omega _1 - omega _2) in an interaction of two coherent states of cavity modes with frequencies (omega _1) and (omega _2). For this process, we calculate the mean number of quanta in the final state in a model with dissipation, which supports the previous result of resonant higher-order harmonics generation in an effective field theory approach (Kopchinskii and Satunin in Phys Rev A 105:013508, 2022).

Wave functions and probability density functions of superposition states of a q-deformed harmonic oscillator are studied. It is found that the intensity of the q deformation parameter and the ratio of probability amplitudes in the superposition state determine the oscillation characteristic of the probability density function. In the Fourier spectrum of the probability density function, high-frequency components disappear as the system evolves to an undeformed state. It is shown that by superposing four-wave functions with the same deformation value (q=0.001), an entangled state having sub-Planck features can be obtained, whereas two deformed states with the same q value do not constitute an entangled state.