The European Physical Journal D最新文献

We have measured several (2p rightarrow 1s) transition energies in core-excited boron-like ions of sulfur and argon. The measurements are reference-free, with an accuracy of a few parts per million. The x-rays were produced by the plasma of an electron cyclotron resonance ion source and measured with a double-crystal x-ray spectrometer. The precision obtained for the measured (1s 2s^2 2p^2~J - 1s^2 2s^2 2p~J') lines is ({approx 3.8},{hbox {ppm}}) for sulfur and ({approx 2.5},{hbox {ppm}}) for argon. The line energies are compared to relativistic atomic structure calculations performed with the mdfgme multi-configuration Dirac–Fock code. This comparison is used for line identification and tests the theoretical methods, which are in agreement with the experimental data up to (49,hbox {meV}). The theoretical calculations have been extended to B, (hbox {C}^+), (hbox {Si}^{9+}), (hbox {Cr}^{19+}) and (hbox {Fe}^{21+}), which were the only B-like ions where such transitions were measured up to now.

Coherent light has revolutionized scientific research, spanning biology, chemistry and physics. To delve into ultrafast phenomena, the development of high-energy, highly tunable light sources is instrumental. Here, the photoelectric effect is a pivotal tool for dissecting electron correlations and system structures. Particularly, above-threshold ionization (ATI), characterized by the simultaneous absorption of several photons leading to a final electron energy well above the ionization threshold, has been widely explored, both theoretically and experimentally. ATI decouples laser field effects from the structural information carried by photoelectrons, particularly when utilizing ultrashort pulses. In this contribution, we study ATI driven by polarization-crafted (PC) pulses, which offer precise scanning over the electron momentum, through an accurate change of the polarization state. PC pulses enable the manipulation of photoelectron momentum distributions, opening up new avenues for understanding and harnessing coherent light. Our work explores how structured light could allow for a proper understanding of emitted photoelectrons momentum distributions in order to distinguish between light structure effects and target structure effects.

We use the Schur concavity of the von Neumann entropy and introduce a majorization-based entanglement criterion for the states of systems consisting of identical fermions. This criterion is in the form of an inequality between the von Neumann entropies of the total density matrix and the single-particle reduced density matrix which have to be satisfied by the separable states of such systems, and therefore, its violation indicates the entanglement. Our criterion is an improved version of the one introduced by Zander et al. (in Eur. Phys. J. D 66: 14, 2012). To illustrate its utility, we use the criterion to various illustrative instances of the families of mixed states and find that when the single-particle Hilbert spaces are of dimension four, the criterion indicates all the entangled states within the families under consideration.

Discovering hidden physical mechanisms of a system, such as underlying partial differential equations (PDEs), is an intriguing subject that has not yet been fully explored. In particular, how to go beyond the traditional method to obtain the PDEs of complex systems is currently under active debate. In this work, we propose a deep-learning approach to discover the underlying Gross-Pitaevskii equations (GPEs) of one-dimensional Bose–Einstein condensates (BECs). The results show that such method is markedly superior to the traditional method due to advantages of the deep neural network. The former possesses the ability to obtain a parsimonious model with high accuracy and insensitivity to data noise, and can successfully discover the underlying GPEs that BECs should obey directly from the data even in the absence of a knowledge structure. More importantly, we find that such method is able to work well even for data with (15%) noise. Although the cases studied are proof-of-concept, the method provides a promising technique for unveiling hidden novel physical mechanisms in quantum systems from observations.

We theoretically analyzed positron affinities (PAs) of acetaldehyde (CH₃CHO) and its deuterated (CD₃CDO) molecules at vibrational excited states with multi-component molecular orbital and vibrational quantum Monte Carlo methods. In the fundamental tone states, the PA value at the C=O stretching vibrational mode of acetaldehyde becomes increased by 9.8 meV (+ 12%) from the vibrational ground state of 84.5 meV, while that at the C-H (aldehyde group) stretching vibrational mode decreased by 2.8 meV ((-)3%). We also confirmed that each vibrational state has a different H/D isotope shift in PA values. Such non-uniformity in quantum vibrational influence on PA values and its H/D isotope shifts dominantly arise from the change in dipole moment by vibrational excitations.

In order to establish important reaction properties, such as rate coefficients, it is often necessary to know the number of reactants that are present in an interaction region. The absolute number densities of pulsed supersonic molecular (NH(_3)) and atomic (H) beams are reported using a laser-based detection method, under a range of experimental conditions including photolysis, Zeeman deceleration, and magnetic focusing. Time-averaged densities of (3.6 ± 2.7) (times ) 10(^4) cm(^{-3}) are reported for successfully Zeeman-decelerated and magnetically focused H atoms, generated by the photodissociation of precursor NH(_3) molecules. Without the magnetic guide components in the beamline, the density of the target radicals of interest is somewhat lower, at (2.5 ± 1.8) (times ) 10(^4) cm(^{-3}). The average density of the undecelerated H atom beam is approximately an order of magnitude higher (2.9 ± 1.9) (times ) 10(^5) cm(^{-3}), with the average density of the molecular ammonia beam over two orders of magnitude higher again (5.1 ± 2.9) (times ) 10(^7) cm(^{-3}). The average number densities measured for the two different species of interest in this work span more than three orders of magnitude. These findings highlight the need for accurate and precise experimental measurements of number densities—for each species of interest, under the appropriate experimental conditions—before doing absolute rate coefficient calculations.