The European Physical Journal D最新文献

Methods of angular momenta are modified and used to solve some actual problems in quantum mechanics. In particular, we re-derive some known formulas for analytical and numerical calculations of matrix elements of the vector physical quantities. These formulas are applied to a large number of quantum systems which have an explicit spherical symmetry. Multiple commutators of different powers of the angular momenta ({hat{textbf{J}}}^{2}) and vector-operator ({hat{textbf{A}}}) are determined in the general form. Calculations of the expectation values averaged over orbital angular momenta are also described in detail. This effective and elegant old technique, which was successfully used by Enrico Fermi and Aage Bohr, is almost forgotten in modern times. We also discuss quantum systems with additional relations (or constraints) between some vector-operators and orbital angular momentum. For similar systems such relations allow one to obtain some valuable additional information about their properties, including the bound state spectra, correct asymptotics of actual wave functions, etc. As an example of unsolved problems we consider applications of the algebras of angular momenta to investigation of the one-electron, two-center (Coulomb) problem ((Q_1, Q_2)). For this problem it is possible to obtain the closed analytical solutions which are written as the ‘correct’ linear combinations of products of the two one-electron wave functions of the hydrogen-like ions with the nuclear charges (Q_1 + Q_2) and (Q_1 - Q_2), respectively. However, in contrast with the usual hydrogen-like ions such hydrogenic wave functions must be constructed in three-dimensional pseudo-Euclidean space with the metric ((-1,-1,1)).

Plasma screening effects on the above-threshold ionization (ATI) of the argon atom in Gaussian windowed soft-core Coulomb (GSC) potential is investigated using the time-dependent Schrödinger equation (TDSE), by employing the Crank–Nicolson numerical method. The variation in the ground-state population and ionization probabilities with time is calculated in the Debye plasma environment. The effect of laser intensity variations on the ATI spectra of argon atom is calculated, and ATI spectra show a similar pattern of redshift, as discussed in the available literature. Plasma screening effects on the population of ground state, ionization probabilities, and ATI spectra of argon atom are studied in GSC potential for the first time, at different laser intensities and Debye lengths.

A tripartite state is said to be a potential resource for secret sharing if in addition to being useful for the secret reconstruction (Singh and Chakrabarty in: Phys Rev A 109(3):032406, 2024), it imposes restrictions on the teleportation fidelity of the bipartite channels associated with three-qubit states (dealer–reconstructor and dealer–assistant channels). It is important to ask the question: for a given class of states satisfying some constraint, which secret sharing resources will have the maximum possible reconstruction fidelity? Here, we address this question for a pure three-qubit GHZ class of states (sometimes referred as Acin states) (Antonio Acín et al. in: J Phys A Math Gen 34(35):6725, 2001; Acín et al. in: Phys Rev Lett 87(4):040401, 2001). We are able to characterize the set of states with maximum possible reconstruction fidelity (called as maximal secret reconstructible state [MSR]). Here, the constraint in characterizing the states is a fixed value of the maximum of the teleportation fidelity of both the bipartite (dealer–receivers) channels. In that spirit our result paves the way in setting the practical information transfer limit in a possible resource theoretic extension of secret sharing. Similarly for a value giving the maximum of Bell-CHSH value of both bipartite channels (dealer–reconstructor and dealer–assistant), we are able to find the maximum achievable reconstruction fidelity. Interestingly, we find that all secret shareable states satisfy Bell’s inequality in both the channels (dealer–reconstructor and dealer–assistant partitions). This brings out a new mutual exclusivity between secret shareable state and Bell’s inequality violation.

We report two-photon excited fluorescence of dyes for refracted laser beams by utilizing tailored laser pulses. A fluorescence contrast difference due to phase shaping could be achieved between different coumarin dyes. Particularly, an increased contrast difference is obtained for configurations close to the Brewster angle. Furthermore, by using a subsequent deformable phase plate for spatial shaping it was possible to precisely adjust the laser beam for controlled refraction at the liquid dye surface. A polarization-dependent refraction was observed when directing the shaped laser beam on the curved liquid adhesion meniscus close to the cuvette wall. This results in a refraction-dependent contrast difference. The presented method could be utilized for surface-sensitive biophotonic imaging applications.

We consider the interaction of a two-level atom with two counter-propagating light pulses of different carrier frequencies. To ensure adiabatic interaction, the pulse duration is much longer than both the inverse frequency difference and the maximum Rabi frequencies of the pulses. For the first time, we examine the case where the atom is initially prepared in a superposition of the ground and excited states with a momentum difference corresponding to one-photon recoil. We identify the conditions under which the atom’s final state is determined by the phase difference of the momentum components of the initial atomic wave. Given the large pulse duration, the interference effects depend critically on the rate of spontaneous emission from the excited state. We analyze the role of spontaneous emission using the Monte Carlo wave function method. The results of our calculations elucidate the influence of spontaneous radiation on both the momentum transferred to the atom and the interference outcome of the two atomic waves.

Reported triple differential cross sections (TDCS) for electron-impact ionization of nitrogen molecule have been calculated by employing distorted-wave Born approximation (DWBA) and independent-atom model (IAM), for incident electron energy of 500 eV, and ejected electron energies of 37 eV, 74 eV, and 205 eV, in coplanar asymmetric geometry. Scattering amplitudes of independent nitrogen atoms calculated in the DWBA were used to determine the TDCS of the molecule in IAM. The obtained results are compared to available experimental and theoretical data. Reasonably good qualitative and quantitative agreement was found for low to intermediate ejected electron energies, in terms of binary and recoil peak prediction. Quantitative discrepancies at higher ejected electron energies are attributed to the DWBA limitations.

Compared to natural chiral structures, planar chiral plasmonic nanostructures, which are two-dimensional artificial structures composed of noble metals that break mirror symmetry, are widely applied in fields such as analytical chemistry, pharmaceutical production, and bioanalytical monitoring. Understanding circular dichroism (CD) and its enhancement mechanisms is crucial for these applications. Although a variety of chiral structures have been extensively studied, a deep understanding of the tunability of the CD effect remains insufficient. In particular, helical structures face challenges such as difficult fabrication and poor tunability. In this study, we designed a chiral structure composed of rectangular metal nanorods and metallic spheres, aiming to achieve a significant tunable CD effect by utilizing the connectivity effect of the metal nanorods, reaching an impressive CD value of 0.7. Results calculated by the finite element method show that, near the resonant wavelengths of 710 nm and 730 nm, the spectral responses of ({T}_{++}) and ({T}_{--}), respectively, exhibit peak and valley patterns, thereby generating a substantial CD effect. Fundamentally, this is due to the shifting of the resonance modes at these specific wavelengths under RCP and LCP light. The extent of this shift can be precisely manipulated by altering the width of the rectangular metal nanorods, thus enabling controlled CD effects. Moreover, the CD effect is found to be highly dependent upon the geometric parameters of the designed structures. In summary, these findings contribute significantly to the development of planar chiral plasmonic nanostructures with tunable and large CD effects, providing valuable insights for their optimization and practical applications.