The European Physical Journal D最新文献

In this roadmap article, we consider the main challenges and recent breakthroughs in understanding the role of carbon molecular nanostructures in space and propose future avenues of research. The focus lies on small carbon-containing molecules up to fullerenes, extending to even larger, more complex organic species. The roadmap contains forty contributions from scientists with leading expertise in observational astronomy, laboratory astrophysics/chemistry, astrobiology, theoretical chemistry, synthetic chemistry, molecular reaction dynamics, material science, spectroscopy, graph theory, and data science. The concerted interdisciplinary combination of the state-of-the-art of these astronomical, laboratory, and theoretical studies opens up new ways to advance the fundamental understanding of the physics and chemistry of cosmic carbon molecular nanostructures and touches on their wider relevance and impact in nanotechnology and catalysis.

A collection of carbon atoms on the road to a fullerene

The transition wavelengths and transition rates of (hbox {W}^{27+}), (hbox {W}^{28+}) and (hbox {W}^{29+}) ions in the 45-65 Å range have been calculated using the flexible atomic code (FAC) package based on the Dirac–Fock–Slater (DFS) method with central potential. By considering a reasonable rate equation, the charge state distributions of (hbox {W}^{27+})-(hbox {W}^{29+}) ions at different electron temperatures were investigated, and the importance of the dielectronic recombination process in the charge state equilibrium was found. In addition, the emission spectra of (hbox {W}^{27+})-(hbox {W}^{29+}) ions in the 45-65 Å in the EAST Tokamak plasma were simulated using a collisional-radiative model. The synthetic spectra show good agreement with the observed in the experiment. Finally, for the diagnostic needs of plasma, some transition pairs that can be used as diagnostic lines are proposed based on the intensity ratio of the transition pair with respect to the electron temperature and density.

Two-photon interference is an interesting quantum phenomenon that is usually captured in two distinct types of experiments, namely the Hanbury Brown–Twiss (HBT) experiment and the Hong–Ou–Mandel (HOM) experiment. While the HBT experiment was carried out much earlier in 1956, with classical light, the demonstration of the HOM effect came much later in 1987. Unlike the former, the latter has frequently been argued to be a purely quantum effect. A generalized formulation of two-particle interference is presented here. The HOM and the quantum HBT effects emerge as special cases in the general analysis. A realizable two-particle interference experiment, which is intermediate between the two effects, is proposed and analyzed. Thus two-particle interference is shown to be a single phenomenon with various possible implementations, including the HBT and HOM setups.

In the generalized view of two-particle interference, independent particles from sources A and B are split into n common channels by the path splitter, and then arrive at detectors (D_1) to (D_n).

We present a method for accurately computing transition probabilities in one-dimensional photoionization problems. Our approach involves solving the time-dependent Schrödinger equation and projecting its solution onto scattering states that satisfy the correct incoming or outgoing boundary conditions. Conventionally, the photoelectron emission spectrum is obtained by projecting the time-evolved wave function onto the stationary continuum eigenstates of the unperturbed, time-independent Hamiltonian. However, when the spatial potential is symmetric, both the initial bound state and the final continuum states exhibit well-defined parity. The propagated wave function retains structural features of the initial bound state, including its parity. As a result, changes in the parity of the continuum states can introduce substantial variations in the projections, leading to spurious oscillations in the computed electron emission spectrum. Our method circumvents this issue by employing scattering states without defined parity. Furthermore, it enables the calculation of directional emission, making it possible to study emission asymmetries. To illustrate the capabilities of our scattering projection method, we analyze the partial differential photoionization probabilities of Al(111) metallic surfaces under short laser pulses at grazing incidence.

Photoelectron spectrum of an aluminum surface. The conventional projection method (thin brown solid line) produces a highly oscillatory spectrum. Smoothing via the standard convolution method (window operator, thick green solid line) results in over-smoothing, eliminating genuine physical oscillations that our method correctly preserves (thick red line).

Arbitrary amplitude dust ion acoustic solitons (DIASs) in plasma consisting of positive ions, regularized kappa distributed electrons and negatively charged dust grains have been investigated by the Sagdeev pseudopotential method. It is found that negative DIASs exist only in a certain range of spectral index (kappa ) and cutoff parameter (alpha ), which increases with the electron concentration. Correspondingly, the region of (kappa ) and (alpha ) for the coexistence of negative and positive DIASs shrinks. In addition, the velocity of soliton decreases with increasing (alpha ) and electron concentration (sigma ), regardless of soliton polarity. On the other hand, the width of positive DIASs decreases with the increase of (kappa ), whereas the one negative solitons take an opposite way. Moreover, the width of DIASs varies non-monotonous with respect to the cutoff parameter. Based on the parameters within Saturn’s magnetosphere, the strength of the electric field with DIAS can explain the observations made within Saturn’s magnetosphere. The present investigation may be useful in the understanding of the properties of localized nonlinear electrostatic structure in space dusty plasma with nonthermal electrons.

Motivated by the prospect of triangular spin cells for quantum information processing, we propose a model featuring spin–orbit interactions on the rungs and magnetic field effects along the legs. Quantum memory can enhance measurement precision for two incompatible observables in the physical system. In this work, we have examined the dynamics of entropic uncertainty and pairwise entanglement for a system of three-spin ( -1/2 ) particles interacting with a quantum memory in the presence of intrinsic decoherence and a non-uniform magnetic field. We employ logarithmic negativity to measure entanglement and study its evolution in a non-uniform magnetic field and decoherence. In addition, we examine and evaluate the operation of the entropic uncertainty relation for non-commuting observables in the three-spin system, analyzing its behavior under identical circumstances. According to the study, entropic uncertainty increases and entanglement decays due to intrinsic decoherence, whereas non-uniform magnetic fields produce complex entanglement patterns. Notably, entanglement and entropic uncertainty can display synchronized oscillatory behavior in specific situations, indicating possible approaches to alleviate decoherence in quantum memories. The fundamental characteristics and constraints of quantum memories are better understood thanks to this work, which also highlights how crucial it is to consider realistic environmental effects when creating quantum technologies.

We present experimental results of characterization of Silicon photomultipliers (SiPM) in a temperature range from 90 mK to 40 K and compare them to room-temperature results. Two SiPMs, one from ONSEMI and one from Hamamatsu Photonics, were tested. Operating voltage ranges, dark count rates, afterpulsing effects and photon detection efficiencies (PDE) were determined with illumination by 275- and 470-nm light fed into the cryostat via an optical fiber. A cryogenic shutter provided a true dark condition, where thermal radiation from room temperature is shielded and the thermal excitations in the chips are frozen. A second tunneling breakdown was observed at this condition, which substantially limits the operating voltage range for the temperatures 20–30 K. Below (sim )5 K, both SiPMs recover to an operating overvoltage range of 3–5 V. We found the chips function through the entire tested temperature range and are capable of withstanding thermal cycling with no major performance degradation.