One of the most enduring and intensively studied problems of x-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed $3C$ and $3D$. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power 2.5 times and the signal-to-noise ratio...
X-ray studies of atomic processes involving highly charged ions at EBIT/S
Ł. Jabłoński, D. Banaś and M. Pajek
Institute of Physics, Jan Kochanowski University, 25-406 Kielce, Poland
The electron beam ion traps and sources (EBIT/S) producing highly charged ions (HCI) offer unique experimental conditions to study various atomic processes [1], including electron impact...
Photoionization plays a key role in the production of highly charged ions in active galactic nuclei (AGNs). The inner shell photoionization leads to highly excited states that are the subject of radiative and Auger cascade. An electron from a higher shell fills the inner-shell vacancy while simultaneously causing the removal of another electron from the atomic system during the Auger decay. As...
Collisional cross sections and collisional-radiative (CR) models are of upmost importance for plasma diagnostics in the entire community, from low-temperature athmospheric pressure plasmas and fusion applications to astrophysical studies. Large efforts have been undertaken to provide collisional data by experiments, simulations, and analytic calculations. However, the validation of collisional...
Emission lines from He-like ions are an essential diagnostics tool of high-resolution X-ray spectra from satellite missions, such as Chandra and XMM-Newton. Due to the simplest close-shell structure of these ions, observable spectra contains the strongest and easiest identifiable emission lines in a variety of astrophysical objects. The physical insight of these lines can be used to probe...
In an electron beam ion trap (EBIT) the ion plasma is confined in a spatially narrow region centered around the electron beam compressed to about 10$^{10}$-10$^{12}$ cm$^{-3}$ densities. The ion cloud in its equilibrium generally consists of a narrow distribution of charge states. This can be finely tuned by adjusting the electron beam energy and current, the axial magnetic field, and the...
Saturated absorption spectroscopy is a tool that can be used to suppress the Doppler broadening of observed atomic and molecular transition lines in order to measure their precise wavelengths. Obtaining a saturated absorption condition by laser excitation is an essential technique for use in saturated absorption spectroscopy. We are introducing the laser excitation process into the collisional...
The study of hyperfine structures in many-electron highly charged ions (HCIs) can provide a deeper understanding of strongly correlated electrons and serve as a benchmark for advanced theoretical calculations. Additionally, the possibility of using HCIs as atomic clock candidates emphasizes the importance of hyperfine structures in many-electron HCIs [1]. However, there has been limited...
The evolution of charge-state-resolved kinetic energy spectra of Sn ions ejected from a laser-produced plasma (LPP) of Sn as a function of the density of the H$_2$ buffer gas surrounding the LPP is investigated. Without a H$_2$ buffer gas, energetic 1 - 5 keV Sn ions in charge states of 4+ up to 8+ are detected. In this keV regime, lower Sn charge states, i.e., below 4+ are absent. When H$_2$...
A detailed understanding of the principles underlying ion-atom and ion-molecule collisions is essential for plasma modelling and diagnostics. Recent advances in experimental techniques have resulted in detailed and highly accurate kinematically complete measurements. However, theory lags far behind and cannot describe the experiments on differential ionisation. In particular, the description...
The problem of low-energy electron-impact rotational excitation of H2 has been studied in great detail over the last 60 years, due to its importance in low-temperature hydrogen plasmas and gases. Be- low 10 eV, rotational excitation comprises up to 20% of the total cross section, and below the v = 0 → 1 threshold (≈ 0:5 eV) it is the dominant contribution to electron energy loss. Accurate...
It has long been observed that the number of weak lines from many-electron atoms follows a power law distribution of intensity. While computer simulations have reproduced this dependence, its origin has not yet been clarified. Here we report that the combination of two statistical models—an exponential increase in the level density of many-electron atoms and local thermal equilibrium of the...
