The European Physical Journal D最新文献

Following up on a recent paper (Bharti et al. in Phys Rev A 109:023110, 2024), we compare the predictions from several R-matrix with time-dependence calculations for a modified three-sideband version of the “reconstruction of attosecond beating by interference of two-photon transitions” (RABBITT) configuration applied to helium. Except for the special case of the threshold sideband, which appears to be very sensitive to the details of coupling to the bound Rydberg states, increasing the number of coupled states in the close-coupling expansion used to describe the ejected-electron–residual-ion interaction hardly changes the results. Consequently, the remaining discrepancies between the experimental data and the theoretical predictions are likely due to uncertainties in the experimental parameters, particularly the detailed knowledge of the laser pulse.

This study is an overview of the atomic data and opacity computations performed by the Atomic Physics and Astrophysics Unit of Mons University in the context of kilonova emission following neutron star mergers, in both the photospheric and nebular phases. In this work, as a sample case, we focus on a specific lanthanide ion, namely Er III. As far as the LTE photospheric phase of the kilonova ejecta is concerned, we present our calculations using both a theoretical method (the pseudo-relativistic Hartree-Fock method, HFR) and a statistical approach (the Resolved Transition Array approach, RTA) to obtain the atomic data required to estimate the Er III expansion opacity for typical conditions expected in kilonova ejecta one day after the merger. In order to draw the limitations of both of our strategies, the results obtained using the latter are compared, and a calibration procedure of the HFR atomic data in this context is also discussed. Concerning the kilonova ejecta nebular phase, atomic parameters that characterize forbidden lines in Er III are calculated using HFR as well as another computational approach, namely the Multiconfiguration Dirac–Hartree–Fock (MCDHF) method. The potential detection of such lines in late-phase kilonova spectra is then discussed.

Solar physicists routinely utilize observations of Ar-like Fe IX and Cl-like Fe X emission to study a variety of solar structures. However, unidentified lines exist in the Fe IX and Fe X spectra, greatly impeding the spectroscopic diagnostic potential of these ions. Here, we present measurements using the Lawrence Livermore National Laboratory EBIT-I electron beam ion trap in the wavelength range 238–258 Å. These studies enable us to unambiguously identify the charge state associated with each of the observed lines. This wavelength range is of particular interest because it contains the Fe IX density diagnostic line ratio 241.74 Å/244.91 Å, which is predicted to be one of the best density diagnostics of the solar corona, as well as the Fe X 257.26 Å magnetic-field-induced transition. We compare our measurements to the Fe IX and Fe X lines tabulated in CHIANTI v10.0.1, which is used for modeling the solar spectrum. In addition, we have measured previously unidentified Fe X lines that will need to be added to CHIANTI and other spectroscopic databases.

We present a two-state Kalman estimator of gravity acceleration and evaluate its performance by numerical simulations and post-measurement demonstration with real-world atomic gravimetry. We show that the estimator-enhanced gravimetry significantly improves upon both short-term sensitivity and long-term stability. The estimates of gravity acceleration demonstrate a (tau ^{1/2}) feature well under white phase noise in the short term, and continue to improve as (tau ^{-1/2}) or improve faster as (tau ^{-1}) in the long term. This work validates the estimation of gravity acceleration as a key topic for future atomic gravimetry.

The performance of atomic gravimetry is limited by noises and other systematic or geophysical effects. By building a Kaman estimator rooted in the physics of atom interferometry, we realize significant improvements in both short-term sensitivity and long-term stability. This demonstration of estimator-enhanced gravimetry would be of great interest for static measurements of gravity, such as metrology or geophysics (Color online)