Single-photon emission associated with double electron capture in F9+ + C collisions

Radiative double electron capture (RDEC), the one-step process occurring in ion-atom collisions, has been investigated for bare fluorine ions colliding with carbon. RDEC is completed when two target electrons are captured to a bound state of a projectile simultaneously with the emission of a single photon. This work is a follow-up to our earlier measurement of RDEC for bare oxygen projectiles, thus providing a recipient system free of electron-related Coulomb fields in both cases and allowing for the comparison between the two collision systems as well as with available theoretical studies. The most significant mechanisms of x-ray emission that may contribute to the RDEC energy region as background processes are also addressed.Comment: Submitted to Phys. Rev.

Charge state evolution in electron beam ion trap

Recently, at the M. Smoluchowski Institute of Physics of the Jagiellonian University a commercial electron beam ion trap (EBIT) was installed for teaching and scientific purposes. The first experiments were focused on observation of radiative recombination and dielectronic recombination. An investigation of higher order resonant recombination processes was also initiated. These recombination processes depend strongly on the charge state of the ions involved in these processes. The EBIT plasma contains always a mixture of different charge states. Therefore, the charge-state distribution of the ions is crucial for the observed atomic processes. A new diagnostics tool for this distribution and a possibility of its manipulation form the main goal of the present paper which may help to better understand the processes investigated with an EBIT

Hypersatellite Kα Production in Trapped Ar Ions at KK Trielectronic Recombination Energies

Funding Information: W.B.-N. acknowledges DSC Grant MNiSzW Nr 7150/E-338/M/2018, the GET_INvolved Programme at FAIR/GSI (www.fair-center.eu/get_involved) and the JIPhD program through contract POWR.03.05.00-00-Z309/17-00. D.S.L.M. acknowledges the Kosciuszko Foundation. P.A and F.G acknowledge the FCT through project number UID/04559/2020 (LIBPhys). Publisher Copyright: © 2023 by the authors.We report measurements of hypersatellite radiation of argon ions in the electron energy region of 5200 eV to 7500 eV. Here, we observed a strong enhancement of this hypersatellite  (Formula presented.)  production. Trielectronic recombination (TR) is discussed as a possible channel for  (Formula presented.)  production leading to this enhancement where main TR resonances are expected to occur. Data analysis was mainly based on the extracted intensity ratio of hypersatellite  (Formula presented.)  to  (Formula presented.)  lines ((Formula presented.)). In addition, the collisional excitation and the collisional ionisation of the K-shell ions were modeled as main background processes of the K (Formula presented.)  X-ray production. The  (Formula presented.) / (Formula presented.)  intensity ratio shows a significant rise around 6500 eV electron energy by a factor of about two above the background level. This observation is compared with calculations of the expected electron energies for the resonant  (Formula presented.)  emission due to the KK TR process. The observed rise as a function of the electron collision energy, which occurs in the vicinity of the predicted TR resonances, is significantly stronger and energetically much wider than the results of theoretical calculations for the TR process. However, the experimental evidence of this process is not definitive.publishersversionpublishe

Towards an Intrinsic Doppler Correction for X-ray Spectroscopy of Stored Ions at CRYRING@ESR

We report on a new experimental approach for the Doppler correction of X-rays emitted by heavy ions, using novel metallic magnetic calorimeter detectors which uniquely combine a high spectral resolution with a broad bandwidth acceptance. The measurement was carried out at the electron cooler of CRYRING@ESR at GSI, Darmstadt, Germany. The X-ray emission associated with the radiative recombination of cooler electrons and stored hydrogen-like uranium ions was investigated using two novel microcalorimeter detectors positioned under 0∘ and 180∘ with respect to the ion beam axis. This new experimental setup allowed the investigation of the region of the N, M → L transitions in helium-like uranium with a spectral resolution unmatched by previous studies using conventional semiconductor X-ray detectors. When assuming that the rest-frame energy of at least a few of the recorded transitions is well-known from theory or experiments, a precise measurement of the Doppler shifted line positions in the laboratory system can be used to determine the ion beam velocity using only spectral information. The spectral resolution achievable with microcalorimeter detectors should, for the first time, allow intrinsic Doppler correction to be performed for the precision X-ray spectroscopy of stored heavy ions. A comparison with data from a previous experiment at the ESR electron cooler, as well as the conventional method of conducting Doppler correction using electron cooler parameters, will be discussed

Radiative double electron capture (RDEC) in ion-atom collisions

Radiative double electron capture (RDEC) observed in collisions of bare ions with atoms is a charge exchange process, during which two target electrons are captured into a bound state of the projectile and a single photon is emitted. This process could be related to the time inverse of double photoionization. For the past twenty years it has been studied, both experimentally and theoretically. However, significant discrepancies between theoretical predictions of the RDEC cross section and experimental results were noted. Here, an overview of the investigation of the RDEC process is given and various theoretical predictions are compared with experimental results

Higher-Order Recombination Processes in Argon Ions Observed via X-ray Emission in an EBIT

In electron–ion collisions, recombination processes play a very important role. Recently, multielectron recombination processes have been highly investigated, as they carry information about electron–electron interaction. Among them, the most basic process is dielectronic recombination (DR). The research presented here was conducted using an EBIT at Jagiellonian University. Using X-ray spectroscopy, we conducted research into K-LL, K-LM, K-LN, K-LO and K-MM resonances. The aim of this study was to investigate the contribution of the intershell higher-order recombination processes in collected spectra. A good resolution for the K-LL DR spectrum made it possible to distinguish structures for He- up to C-like Ar ions

Single-photon emission correlated to double-electron capture by bare ions : background processes

Radiative single- and double-electron capture are one-step processes where a single target electron or two target electrons, respectively, are captured to a bound state of a highly charged projectile with the simultaneous emission of a single photon. In ion–atom collisions, several background processes are likely to contribute to these processes and may interfere with the measured x-rays due to radiative single and double capture. In this study, possible contributions from radiative electron capture to the continuum, secondary electron bremsstrahlung, the two-step process of independent double radiative electron capture, as well as radiative- combined with nonradiative-electron capture are taken into account based on our analysis of the data for 2.21 MeV u−1 F9+ ions colliding with a thin carbon foil

X rays coincident with single and double capture in F^{8,9+} + C collisions

X rays emitted from fluorine in single and double capture collisions with carbon have been studied. Fluorine K-x-ray emission and radiative electron capture have been observed with differences depending on the initial projectile charge state (F^{9+} or F^{8+}) and whether single or double capture occurs. These origins of these differences are considered