Table of contents

This volume contains the proceedings of the 16th International Conference on the Physics of Highly Charged Ions (HCI 2012) held at the Ruprecht-Karls University in Heidelberg, Germany, 2–7 September 2012 (figure 1). This conference has been part of a biannual conference series that was started in Stockholm in 1982 and, since then, has been organized at various places around the world, with recent venues in Belfast (UK, 2006), Tokyo (Japan, 2008) and Shanghai (China, 2010).

The physics of highly charged ions (HCI) is a rapidly developing and attractive field of research with impact upon many other research disciplines. Apart from fundamental studies on the structure and dynamics of matter in extreme fields, or the search for physics beyond the standard model, detailed knowledge about the properties and behavior of HCI is crucial for other areas, from astro- and solar physics to hot plasma and fusion research to extreme ultra-violet and ion lithography, or even to medical research, to name just a few. In fusion research, for example, of whether tokamak, stellarator or confinement fusion facilities, most models and diagnostics deeply rely on the understanding of HCI and the (theoretical) prediction of accurate atomic data for these systems. In life science, moreover, ion therapy or the laser acceleration of ions and electrons may help save and improve the quality of life in the future. Many of these and further topics are addressed in these proceedings.

After 30 years, the HCI conference series, and especially the meeting in Heidelberg, is appreciated much as a key forum for bringing together senior experts with students, young researchers and scientists from related disciplines who make use and give back impact upon the research with HCI. More than 250 scientists from 23 countries participated in HCI 2012 and presented the current status of the field. About one third of them were post-graduate students, showing that the field attracts many young and talented physicists.

The conference was held in the Physics Lecture Hall at the New Campus of Heidelberg University. On the evening of 2 September, the day before the opening of HCI 2012, all participants were welcomed warmly at the foyer of this lecture hall, whose decorative glass front provides a view upon artificial ponds and water lilies at this time of the year. For many colleagues and delegates, this evening offered a hearty re-encounter with each other, along with wine and other beverages. The conference then opened on the morning of 3 September, and an exciting program was organized by the local committee with the help of the International Advisory Board, including 5 invited talks, 10 progress reports as well as 26 selected talks. In addition, more than 230 posters were presented in two sessions, with beer and brezels aside. On Tuesday evening, an exciting public lecture on Heavy ions in therapy and space was given by Marco Durante from the GSI Helmholtz Center and Technical University in Darmstadt. Moreover, many of the participants joined the guided tour through the old city of Heidelberg with its famous (ruins of the) castle, and several the Solar Boat Trip. On Thursday night, we all enjoyed the conference dinner with home-brewed beer and regional specialties at the 'Kulturbrauerei' in the historic center of Heidelberg. Finally, scientific tours were also organized to GSI Darmstadt and the Max-Planck Institute for Nuclear Physics in Heidelberg on the last day of the conference, and attracted much consideration.

We here present the proceedings of this conference that contain a total of 104 contributions, including invited papers, progress reports and contributed papers. As previously, these papers are grouped into five categories.

(1) Fundamental aspects, structure and spectroscopy.

(2) Collisions with electrons, ions, atoms and molecules.

(3) Interactions with clusters, surfaces and solids.

(4) Interactions with photons, plasmas and strong field processes.

(5) Production, experimental developments and applications.

All papers were refereed by senior delegates to the conference, and we like to thank all of them for their work and rapid response.

The next conference in this series will be held in Bariloche, Argentina, at the beginning of September 2014 for which we wish the organizers great success. Looking forward seeing you again in 2014.

Acknowledgments

Much of the success of the conference was due to the continuous support of the Advisory Board, the Local Organization Committee and the financial support by various academic and industrial sponsors. In particular, we wish to acknowledge the generous support by the Wilhelm-and-Else Heraeus Foundation, The International Union of Pure and Applied Physics (IUPAP) and the Heidelberg Center for Quantum Dynamics. We thank all of them, and especially Stefanie Lüttges and Natali Jurina and her team from UniTT Conference Management. The assistance of Hans-Georg Siebig is very much appreciated. Finally, many thanks also to the post-graduate students from the Department of Physics and Astronomy in Heidelberg, who helped with customizing the conference site and running the audio-visual equipment.

For over a decade, the x-ray astrophysics community has enjoyed a fruitful epoch of discovery largely as a result of the successful launch and operation of the high resolution, high sensitivity spectrometers on board the Chandra, XMM-Newton and Suzaku x-ray observatories. With the launch of the x-ray calorimeter spectrometer on the Astro-H x-ray observatory in 2014, the diagnostic power of high resolution spectroscopy will be extended to some of the hottest, largest and most exotic objects in our Universe. The diagnostic utility of these spectrometers is directly coupled to, and often limited by, our understanding of the x-ray production mechanisms associated with the highly charged ions present in the astrophysical source. To provide reliable benchmarks of theoretical calculations and to address specific problems facing the x-ray astrophysics community, electron beam ion traps have been used in laboratory astrophysics experiments to study the x-ray signatures of highly charged ions. A brief overview of the EBIT-I electron beam ion trap operated at Lawrence Livermore National Laboratory and the Max-Planck-Institut für Kernphysik's FLASH-EBIT operated at third and fourth generation advanced light sources, including a discussion of some of the results are presented.

We have observed the emission spectra in collisions of bare oxygen ions with a helium gas target in the soft x-ray region with a window-less silicon drift detector at the collision energy range of 48–80 keV. The dominant soft x-ray emission corresponds to the 1s–2p transition of hydrogen-like oxygen O⁷⁺ produced by the single-electron charge exchange reaction. Other emission lines are the 1s–3p, 1s–4p and 1s–5p transitions of O⁷⁺, and also the 1s²–1s2p transition of O⁶⁺ produced by the true double-electron capture. The cascades from the upper states result in a large population of the 2p state, even though the direct capture into the 2p state is extremely scarcer than those into the 3p, 4p and 5p states.

In observations of Capella, the x-ray ultraviolet (XUV) emission compared to the extreme ultraviolet (EUV) emission significantly exceeds expectation from collisional–radiative spectral modeling. This discrepancy is presently undergoing experimental verification at an electron beam ion trap. An important step of the procedure is the relative efficiency calibration of spectroscopic detection equipment for EUV and XUV observations, for which we use the branching ratio of 1s–3p and 2s–3p transitions in the H-like spectrum O VIII. We present high-resolution measurements and associated modeling of the O VIII emission near 102 Å, which consists not only of the two 2s–3p transitions, but also of two 2p–3s and three 2p–3d transitions.

We report on two-level laser spectroscopy on the electron dipole-forbidden 1s²2s²2p ²P_3/2–²P_1/2 transition in boron-like Ar¹³⁺ ions stored in an electron beam ion trap. By monitoring the laser-induced fluorescence as a function of the laser frequency, the transition wavelength was determined to be 441.25575(17) nm. The accuracy achieved in this first investigation is equal to that of the best wavelength measurements in highly charged ions.

The Lamb shift in medium-heavy H-like and He-like ions has been determined with unprecedented accuracy with a novel x-ray spectroscopy technique. Absolute wavelength measurements of emission lines from trapped highly charged Ar ions thereby achieved uncertainties down to the range of 1.6–2.4 ppm. For the H-like ion Ar¹⁷⁺, the ground state Lamb shift is determined with a 0.4% accuracy, thus excellently confirming quantum electrodynamics (QED) calculations and therefore the hitherto implied suitability of lines from these ionic species as absolute and accurate standards in the x-ray region. Second-order QED terms, i.e. two-electron terms, are also probed for the He-like species Ar¹⁶⁺. Deviations from QED predictions that have recently been claimed are excluded with high significance by the present results.

We present K-shell x-ray spectra of highly ionized Mg acquired with the EBIT calorimeter spectrometer at a resolution of 4.5 eV in charge exchange recombination experiments using the LLNL EBIT-I electron beam ion trap. We measured the Doppler width of Mg¹¹⁺ Lyα in the same experiments using a high resolution crystal spectrometer, giving an estimate of the ion temperature. We find hardness ratios for Mg¹¹⁺ ranging from 0.6 to 1.6, depending on the neutral gas target. In most of the experiments, the ion temperature was ∼ 10–15 eV amu⁻¹, indicating that the variations in hardness ratio are intrinsic to the choice of neutral target gas, and are not simply a consequence of variations in the collision velocity resulting from evaporative cooling of the trapped ions. The spectral variations show that high resolution x-ray spectroscopy is highly diagnostic of charge exchange reactions, but requires well-developed theory to interpret.

We have made high-resolution measurements of the iron L-shell emission near 15 Å using the EBIT-I electron beam ion trap at Livermore that exhibit L-shell transitions from autoionizing levels in Fe¹³⁺, Fe¹⁴⁺ and Fe¹⁵⁺ ions. The observed L-shell iron spectra were modeled using the flexible atomic code augmented with transition energies produced by calculations based on the relativistic multi-reference Møller–Plesset (MRMP) perturbation theory, allowing us to identify multiple M-shell iron lines. Our measured values for the Fe XV emission lines are in excellent agreement with a recent measurement using the BESSY-II synchrotron but the present measurements have somewhat higher accuracy. Our MRMP calculations are compared to earlier calculations using the many-body perturbation theory approach, and we find good agreement for some but not all transitions.

Strong, relatively short, absorption dips have been observed in the x-ray light curves measured from the high mass x-ray binary system Cygnus X-1. With increasing strength of the dips, which are believed to be caused by 'clumps' of cold material present in the stellar wind of Cyg X-1's companion star, K-shell absorption lines in L-shell ions of Si and S develop. To determine the bulk motion of the clumps via the Doppler shifts of these lines with high accuracy, we measured their reference energies using the Lawrence Livermore National Laboratory electron beam ion trap EBIT-I and EBIT Calorimeter Spectrometer. Our findings—shifts consistent with zero velocity of the absorber throughout all ionization states at orbital phase zero—provide evidence for an onion-like ion structure of the clumps.

We have measured the projectile x-rays from 56 MeV sulphur ions in collision with thin carbon foils using a high-resolution bent-crystal spectrometer. The resolution of the spectrometer is good enough to resolve lines arising from transitions in H-, He- and Li-like ions. The line energies are compared with values from the NIST x-ray database. The data have also been used to generate the approximate equilibrium charge state distribution, which is compared with semi-empirical model predictions.

We present visible spectra of highly charged tungsten ions observed with a compact electron beam ion trap (EBIT). Several transition lines previously observed with the Tokyo EBIT (Watanabe et al 2012 Can. J. Phys.90 497) have been reproducibly observed. By observing the electron energy dependence in detail, the charge state of the ion responsible for those lines is identified.

Atomic spectra emitted by fusion plasmas are generally contaminated by ions originating from plasma erosion of material walls. These ions may be present in several charge states and the radiation they emit falls in the x-ray to vacuum ultraviolet regions, making them atomic fingerprints used as a diagnostic tool. This work reports on recent achievements on the interpretation of specific tungsten spectra from the Axially Symmetric Divertor Experiment (ASDEX) Upgrade tokamak and the Large Helical Device (LHD) stellarator.

Measurements of extreme ultraviolet radiation from gadolinium, dysprosium and tungsten ions with an open n = 4 shell were performed at the National Institute of Standards and Technology. The ions were produced and confined in an electron beam ion trap, and the spectra were recorded with a flat-field grazing-incidence spectrometer in the wavelength range 3.5–17.5 nm. These data are useful for the development of future lithography sources and for diagnostics of hot plasmas in fusion devices.

We present extreme ultra-violet emission spectra of highly charged gadolinium ions obtained with an electron beam ion trap at electron energies of 0.53–1.51 keV. The electron energy dependence of the spectra in the 5.7–11.3 nm range is compared with calculation with the flexible atomic code.

The ARTEMIS experiment at GSI aims at high-precision measurement of the Zeeman splitting in boron-like argon. Splittings of both ground ²P_1/2 and nearest excited ²P_3/2 states will be accessible. The most accurate up-to-date values of the g factor of these states including the interelectronic interaction, quantum electrodynamical and recoil effects are presented. The higher-order magnetic field contributions to the Zeeman splitting are investigated as well.

High-precision calculations of 1s²2s2p excited energy levels in Be-like Kr isotopes are presented using the multi-configuration Dirac–Fock approach. The calculations include QED corrections and electron correlation including all single and double excitations up to n = 5 orbitals. Breit interaction and vacuum polarization were included to all orders in the self-consistent process. Effects of isotopic mass shifts and hyperfine corrections for ⁸³Kr are discussed.

The long sought after ground-state hyperfine transition in lithium-like bismuth ²⁰⁹Bi⁸⁰⁺ was observed for the first time using laser spectroscopy on relativistic ions in the experimental storage ring at the GSI Helmholtz Centre in Darmstadt. Combined with the transition in the corresponding hydrogen-like ion ²⁰⁹Bi⁸²⁺, it will allow extraction of the specific difference between the two transitions that is unaffected by the magnetic moment distribution in the nucleus and can therefore provide a better test of bound-state QED in extremely strong magnetic fields.

Current progress in ab initio QED calculations of the hyperfine structure and the g-factor of highly charged Li-like ions is presented. Special attention is paid to the recent evaluation of the two-photon exchange corrections in the presence of a magnetic field. The most accurate theoretical values for the specific difference between the hyperfine splittings of H- and Li-like bismuth ions as well as for the g-factor of the Li-like silicon ion are presented.

Ab initio calculation of the two-electron vacuum-polarization corrections to the hyperfine splitting in Li-like bismuth is presented. The diagrams with electric and magnetic vacuum-polarization loops are evaluated rigorously to all orders in αZ. The accuracy of the theoretical prediction for the screened quantum electrodynamics contribution to the specific difference of the hyperfine splitting values of H- and Li-like bismuth is improved by a factor of 3.

Relativistic theory of the nuclear recoil effect in highly charged Li-like ions is considered within the Breit approximation. The normal mass shift (NMS) and the relativistic NMS (RNMS) are calculated by perturbation theory to zeroth and first orders in the parameter 1/Z. The calculations are performed using the dual kinetic balance method with the basis functions constructed from B-splines. The results of the calculations are compared with the theoretical values obtained by other methods.

Transition probability values from the 1s²2s3p ³P₀ level for selected beryllium-like ions, from Z = 5 to 92, are calculated using the multi-configuration Dirac–Fock method including QED corrections, and full correlation up to the 4f subshell in both initial and final levels, for 1s²2s3s ³S₁, 1s²2s2p ³P₂ level and 1s²2p^2 3P₁ decay modes of this level.

The structure of satellite (additional vacancies in N and/or O shells) and hypersatellite (additional vacancies in M or M and N shells) Mα_1,2 and Mβ₁ lines in the x-ray spectra of heavy atoms can be explained precisely by taking into account the extensive multiconfiguration Dirac–Fock calculations. The presented results are a precursor for the reliable quantitative interpretation of a very complex origin structure of Mα_1,2 and Mβ₁ lines in various high-resolution x-ray spectra of heavy atoms induced by different light and heavy projectiles. Moreover, the intensities of the M-x-ray lines of uranium can be helpful in the application of x-ray measurements from UO₂ as a reference material (virtual standard) for non-destructive wavelength-dispersive electron probe microanalysis.

The precise determination of the energy of the Lyman α1 and α2 lines in hydrogen-like heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields. To improve the experimental precision, the new detector concept of microcalorimeters is now exploited for such measurements. Such detectors consist of compensated-doped silicon thermistors and Pb or Sn absorbers to obtain high quantum efficiency in the energy range of 40–70 keV, where the Doppler-shifted Lyman lines are located. For the first time, a microcalorimeter was applied in an experiment to precisely determine the transition energy of the Lyman lines of lead ions at the experimental storage ring at GSI. The energy of the Ly α1 line E(Ly-α1, ²⁰⁷Pb⁸¹⁺) = (77937 ± 12_stat ± 25_syst) eV agrees within error bars with theoretical predictions. To improve the experimental precision, a new detector array with more pixels and better energy resolution was equipped and successfully applied in an experiment to determine the Lyman-α lines of gold ions ¹⁹⁷Au⁷⁸⁺.

We measured the radiative lifetime of the ¹S₀ metastable state of Kr²⁺. This state dominantly decays to the ³P₁ state via a magnetic dipole transition. The lifetime was determined by measuring emitted photons (350.5 nm) as a result of the ¹S₀ → ³P₁ decay of Kr²⁺ stored in an electrostatic ion trap. The obtained radiative lifetime was 15.3 ± 0.9 ms, which agrees with the experimental value reported by Calamai and Johnson (1992 Phys. Rev. A 45 7792) within experimental error.

In recent years for the fundamental theory of quantum electrodynamics, considerable progress in the evaluation of higher order corrections has been achieved—not only for hydrogen—but also for helium-like systems—up to very heavy nuclei. We were aiming at a more precise determination of the lifetime of the metastable 2 ³P₀ state in He-like uranium which has a calculated value of 57.3 ps [1, 2]. From the lifetime it is possible to derive the energy of the state. In October 2011 we were able to perform a first test experiment at GSI, Darmstadt to study the feasibility of a new experimental detection technique. This advanced set-up consists of two state-of-the-art energy-, time- and position-sensitive germanium detectors [3] in combination with collimators in a Soller-slit like assembly. A beam of U⁹¹⁺-ions at an energy of 290 MeV u⁻¹ is passed through a thin nickel foil in the interaction chamber. From the decrease in intensity as a function of the target distance one may extract a decay curve from which the lifetime can be derived. The advantages of this new set-up, in comparison to former experiments [4, 5] will be discussed and the results of a preliminary data analysis will be presented.

A brief overview is presented in this paper on some experiments conducted at the Experimental Storage Ring (ESR) of GSI which addressed the β decay of stored and cooled highly charged ions. Special emphasis is placed on the two-body beta decay of bare or few-electron ions: bound-state β⁻ decay (β_b) and its time-mirrored counterpart, orbital electron capture. The former decay mode was detected experimentally 20 years ago at the ESR. The latter could be investigated there for the first time in detail for the simplest quantum systems: hydrogen- and helium-like atoms. The main results of these experiments will be presented. Also their impact on stellar nucleosynthesis, in particular the s-process, is discussed.

In recent years several measurements of the orbital electron capture half-lives of few-electron ions have been carried out employing the storage ring ESR at GSI. Hydrogen-like and helium-like ¹⁴⁰Pr and ¹⁴²Pm as well as hydrogen-like ¹²²I were studied. Half-lives of the corresponding fully ionized nuclides provide the three-body β⁺ decay constants.

A novel scheme is proposed for studying the parity-violating (PV) effects in beryllium-like heavy ions. It is based on the application of circularly polarized ultraviolet light for inducing a single-photon transition between the metastable 1s²2s2p ³P₀ and the short-lived 1s²2s2p ³P₁ states. We argue that the cross section of such a photoabsorption process is sensitive to the mixing between the allowed magnetic dipole (M1) and the PV electric dipole (E1) excitation channels. Based on relativistic calculations, we find that the PV-mixing may influence the cross section at the level of 10⁻⁵% for beryllium-like uranium, U⁸⁸⁺.

Quasidegenerate states of different parity for heavy Li-like ions are studied to search for the enhancement of the parity non-conservation (PNC) effects. The energies of the states $\left (1\mathrm {s} 2\mathrm {s} n\kappa \right )_{1/2}$ and $\left ( 1\mathrm {s} 2\mathrm {p}_{1/2} n\kappa \right )_{1/2}$ with κ = ± 1 and 4 ⩽ n ⩽ 7 are evaluated in the range Z = 54–100. The PNC admixing parameter has been calculated for the states with n and κ, which seem most promising for increasing the PNC effect. The PNC effect is evaluated for the process of dielectronic recombination of a polarized electron with a helium-like ion.

The K-shell ionization cross sections of Al induced by H⁺ and Ne⁷⁺ were studied. The ionization cross sections obtained are compared with the predictions of ECPSSR theory (based on the perturbed-stationary-state approach including Coulomb deflection, energy loss and relativistic corrections), BEA (binary encounter approximation) and 1sσ molecular-orbital ionization. It is found that the ECPSSR theoretical results agree with the experimental data very well for proton impact, while the BEA model with correction of Coulomb deflection shows good agreement with experimental results.

We have investigated the dependence of electron capture to the continuum (ECC) on the longitudinal momentum of recoil ions in the transfer ionization of 120 and 300 keV He²⁺ on argon collisions. Compared with theoretical lines predicted by the kinematical relationship between longitudinal momentum of recoil ions and ECC electrons, it is shown that the electron is mainly transferred to the first excited state of He⁺ ions. The experimental data also show that the electron capture to the ground state of He⁺ is accompanied by target excitation, where the target excitation results from direct excitation in the transfer ionization processes.

Experimental and theoretical results for electron emission in 440 keV u⁻¹ Li⁺ with He targets are presented. Theoretical cross-sections are obtained using extensions of the continuum distorted wave and the continuum distorted wave-eikonal initial state models to the case of dressed projectiles and a four-body classical trajectory Monte-Carlo. The contributions of electron emission from the different aggregates of the collision system are investigated.

The atomic processes of charge exchange and ionization in collisions between fully ionized ions (C⁶⁺, N⁷⁺) and atomic hydrogen (H(1s), H(n = 2)) are studied theoretically in the intermediate–high collision energy range (10–500 keV amu⁻¹). The method employed is the so-called classical trajectory Monte Carlo method.

We present total cross sections for ionization, and total and nl-partial cross sections for electron capture in collisions of Kr³⁶⁺ and W⁶⁰⁺ with H(1s). Calculations have been carried out using the classical trajectory Monte Carlo method. We have found that scaling laws as functions of the ion charge are valid for total electron capture cross sections, but they are less accurate for n-partial cross sections. The nl-partial cross sections show l distributions similar to those found for collisions with Ar¹⁸⁺ by Errea et al (2006 J. Phys. B: At. Mol. Opt. Phys.39 L91).

From the measured target thickness dependence of the K x-ray and radiative electron capture (REC) yields in the 0.75–2.5 MeV u⁻¹³²S, ³⁵Cl + Cu collisions, the cross sections for K x-ray production and REC, in dependence on collision energy, have been determined. In comparison with theory, we find simple models that describe rather well some of the present results. The target (Cu) K x-ray production cross sections are in fair agreement with ECPSSR model predictions. The REC theoretical calculations (Stobbe model times 11, the number of loosely bound electrons in Cu) are in agreement with the present data for Cl + Cu collision, but overestimate the data for S + Cu collision by approximately a factor of 2. Large enhancements for the projectile K-shell fluorescence yields, up to 10 for S and 6 for Cl, as well as for K-shell vacancy lifetimes, up to 16 for S and 21 for Cl, are reported.

We study charge-transfer reactions between slowly moving, highly charged ions and neutral atoms using an energy-loss spectroscopy method. In this study, Xe^q+ (q = 4–11) ions (incident energy: 5.0 keV) are used as the incident ions and Ar as the target atom. Transfer-ionization (TI) processes are identified for one-electron capture reactions by application of a coincidence technique. We find that the TI process represents approximately 25% of the total one-electron capture reaction for $q\geqq 8$. The measured energy gains agree well with theoretical predictions for one-electron capture, but the agreement between the measured and theoretical energy gains is not as good for two-electron capture processes.

X-ray yields for the projectile L-shell have been measured for collisions between Xe²⁰⁺ and thick solid targets throughout the periodic table with incident energies near the Bohr velocity. The yields show a very pronounced cyclic dependence on the target atomic number. This result indicates that Xe L x-ray emission intensity is greatly enhanced either in near-symmetric collisions or if the binding energy of the Xe M-shell matches the L- or N-shell binding energy of the target.

We present calculations of the total and m-fold electron-loss cross sections using the DEPOSIT code for highly charged U^q+ ions (q = 10,31,33) colliding with Ne and Ar targets at projectile energies E = 1.4 and 3.5 MeV u⁻¹. Typical examples of the deposited energy T(b) and m-fold ionization probabilities P_m(b) used for the cross-section calculations as a function of the impact parameter b are given. Calculated m-fold electron-loss cross sections are in good agreement with available experimental data. Although the projectile charge is rather high, the contribution of multiple-electron-loss cross sections to the total electron-loss cross sections is high: about 65% for the cases mentioned.

The absolute double differential cross sections (DDCS) have been obtained for electron emission from oxygen molecules under the impact of bare carbon ions. The DDCS values are measured between an energy range of a few eV to 600 eV and over an angular range of 30–150°. These are then compared with the continuum distorted wave-eikonal initial state (CDW-EIS) calculations. The DDCS values for O₂ are divided by that of atomic oxygen (calculated theoretically) to look for any oscillatory behaviour arising from Young-type interference. In addition, the DDCS ratios are further divided by a fitted straight line to extract any primary interference oscillation. Although a negative result has been obtained, these observations are in qualitative agreement with the prediction of the CDW-EIS model used.

We have precisely measured absolute double differential cross sections (DDCSs) for secondary electron emission produced in collisions of 6.0 MeV u⁻¹ C⁶⁺ and C⁴⁺ ions with water vapor. Theoretical calculations of the DDCSs were made for C⁶⁺ ions using the continuum distorted wave-eikonal initial state model (CDW-EIS) in its straight-line version of the impact parameter approximation, showing general good agreement with experimental data, except in the intermediate- and high-energy region (> 50 eV), particularly at the backward angles (> 110°). On the other hand, the single differential cross section (SDCS), which was obtained by integrating the measured DDCSs over the solid angle, showed fairly good agreement with the CDW-EIS in the low-energy region (< 200 eV), while a significant discrepancy between the observed SDCS and the Rudd-model scaling (× 36) can be seen, suggesting that a simple Z²-scaling law (i.e. first Born approximation) is not applicable for high-Z bare projectiles such as C⁶⁺ ions. The SDCS of C⁴⁺ ions was observed to be smaller than that of C⁶⁺ ions by  ∼ 50% in the low-energy region (< 200 eV) due to the screening effect of its bound electrons in C⁴⁺ ions, which could be explained quantitatively by taking account of an effective projectile charge.

Single ionization from water molecules by impact of bare ions is studied. Different approximations are employed, within the post and prior versions of the continuum distorted wave–eikonal initial state model, to calculate double differential cross sections. Post–prior discrepancies are observed between theoretical results. The sensitivity of the calculations to the description of the initial bound orbitals is investigated.

Using the translational energy-gain spectroscopy technique, we have measured the energy-gain spectra and absolute total cross sections for single-electron capture in collisions of Ne²⁺ with N₂, CO₂ and H₂O at laboratory impact energies between 50 and 400 eV and 0° scattering angles. In all the collision systems studied here, reaction channels have been observed which indicate the presence of the long-lived metastable states of (2s² 2p^4 1D and ¹S) in the Ne²⁺ incident beam. These measurements also indicate that capture from the metastable states into excited states of the projectile product ions is the most important inelastic process. Contributions from capture accompanied by the excitation and ionization of the target product are also detected. In addition, the energy dependence of the total single-electron capture cross sections is studied and found to slowly increase with increasing impact energy. The present data are compared with the theoretical calculations of the classical over the barrier, extended classical over the barrier and Landau–Zener models.

We report on the fragmentation of anthracene molecular ions C₁₄H₁₀^r+ as a function of the parent ion initial charge r (= 1–4). Neutral anthracene molecules in the gas phase were ionized and excited in collisions with Ar⁸⁺ ions at 40 keV and the mass-to-charge spectra of the parent ions C₁₄H₁₀^r+ (1 ⩽ r ⩽ 4) were obtained. Stable molecular ions C₁₄H₁₀^r+ (1 ⩽ r ⩽ 3) are observed. Branching ratios for the competitive evaporation (loss of neutral fragments) and fragmentation (charge separation) processes were measured for C₁₄H₁₀²⁺ parent ions. For C₁₄H₁₀³⁺ parent ions, the results indicate that fragmentation is the only dominant process and quasi-symmetric fission is observed.

Multiple ionization dynamics of rare gas dimers by slow highly charged ions has been investigated using the three-center Coulombic over-barrier model. The outermost electrons at two atomic sites in the dimer are sequentially removed by forming a quasi-molecule with a projectile, where partial screening is taken into account in the non-active site ionized during a collision. It is found that the fragment ion pair (Q,Q') distribution is remarkably sensitive to the screening effect, which enhances the population of highly charge-asymmetric pairs such as (2,0) and (3,1). Recent measurement of the ion pair distribution in Ar⁹⁺ + Ar₂ collisions is best reproduced with the present model by taking a screening parameter of s = 0.4.

Absolute non-resonant recombination (RR) rate coefficients of Ni¹⁹⁺ ions were measured by employing the electron–ion merged-beams technique at the main cooler storage ring in Lanzhou. Using the electron cooler and energy detuning system, we obtained a narrow momentum spread (Δp/p ∼ 2 × 10⁻⁴) and tuned precisely relative energies (minimum electron energy detuning step voltage 1 V) between electrons and ions. In addition, we compared the RR rate coefficients with the theoretical ones calculated by the self-consistent-field Dirac–Slater method, and found that they are in good agreement.

We report on the calculations of the K-shell differential radiative recombination (RR) rate coefficients for very low, in the range of meV, relative electron–ion energies. The rate coefficients were derived for bare uranium ions colliding with free electrons both within the nonrelativistic dipole approximation and using fully relativistic calculations. We show that even for such low relative ion–electron energies, the differential rate coefficient reveals strong relativistic effects. We demonstrate that the measurements of the relative electron energy dependence of the RR rates represent a very sensitive tool for precise studies of the RR process and, in particular, for probing the fine details of the relativistic effects in the RR of ions with electrons. The results are discussed in the context of the first x-ray state-selective RR experiment performed for very low relative electron–ion energies.

The sequential radiative recombination of initially bare ions, which are collided with two spatially separated electron targets, is studied. It is demonstrated that the magnetic sublevel population of H-like ions, which are formed due to electron capture from the first target, depends on the first radiative recombination (RR) photon emission direction. Such a relative population, which can be parameterized in terms of the polarization parameters, affects then the angular and polarization properties of the second photon emitted in the collision with the second target. The coincidence γ–γ RR measurements may allow us to study, therefore, the process in which (i) H-like ions of some particular polarization are 'selected out' of the beam by detecting first recombination photons and (ii) this polarization is 'measured' in the second electron capture process. In order to describe the output of the (future) γ–γ correlation measurements, we derive the general expression for angular- and polarization-correlation function. Detailed calculations for the dependence of this function on the experimental setup and collision energy are performed for the RR of bare uranium ions.

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.

Radiative double electron capture is a fundamental atomic process which should be observed in collisions of bare ions with atoms, albeit with a much smaller cross-section than single radiative electron capture. A new experiment—to observe this rare process under single-collision conditions—has been performed at the internal gas jet target of the experimental storage ring at GSI in Darmstadt. X-ray spectra associated with single and double charge exchange have been observed in 30 MeV u⁻¹ collisions of bare chromium ions (Cr²⁴⁺) with helium and nitrogen target gases.

In this paper, we present recombination rate coefficients for astrophysically relevant B-like C and B-like Ne ions, recently measured at the CRYRING electron cooler. The investigated energy ranges covered the dielectronic recombination resonances of 2s–2p (△n = 0) core excitations for both the ions. The experimental rate coefficients are compared with the results from AUTOSTRUCTURE calculation. Temperature-dependent plasma rate coefficients from 10³ to 10⁶ K are obtained from the recombination spectra by convolution with Maxwell–Boltzmann energy distributions. The experimental plasma rate coefficients of B-like C show good agreement with the calculations at high temperatures, while at low temperatures, the calculated results severely underestimate the plasma rate coefficients. In the case of B-like Ne, the agreement between experimental and calculated results is rather good (within the experimental uncertainties) over the presented temperature range.

The utilization of the resonant atomic electron–ion collision process of dielectronic recombination (DR) as a tool to probe nuclear properties via isotope shifts and hyperfine effects is discussed. Based on DR, this resonance reaction spectroscopy at electron coolers of heavy-ion storage rings denotes a versatile approach to access nuclear parameters such as charge radius, spin, magnetic moment or lifetimes of long-lived excited nuclear states (isomers). The high sensitivity of DR allows for experiments with artificially synthesized rare isotopes and isomers. Recent experimental progress in the preparation of such exotic species at the ESR storage ring in Darmstadt is presented. The DR technique is exemplified for the case of ²³⁴Pa⁸⁸⁺ (Z = 91).

Polarization correlations between photons emitted in dielectronic recombination (DR) of initially hydrogen-like ions are analysed based on a density matrix approach and relativistic Dirac's theory. Special attention is given to the non-dipole contributions in the photon field expansion of the electron–photon interaction. In particular, we apply our general formalism to the radiative decay of the L_1/2L_3/2 resonance that is formed in DR of (initially) hydrogen-like uranium ions. The corresponding calculations show that a mixing between the leading electric dipole (E1) and the magnetic quadrupole (M2) transitions can significantly affect the polarization correlations between the emitted photons.

Theoretical and experimental investigations of higher-order electron–ion recombination resonances including inter-shell excitations are presented for L-shell ions of Kr with the aim of examining details of atomic structure calculations. The particular importance of electron–electron interaction and configuration mixing effects for these recombination processes enables their use for detailed tests of electron correlation effects. A test of the required level of considered mixing configurations is presented and further experiments involving higher-order recombination channels are motivated.

Relativistic calculations of inner-shell atomic processes in low-energy Ne–F⁸⁺(1s) and Xe–Xe⁵³⁺(1s) collisions are performed. The method of calculation exploits the active-electron approximation and is based on the coupled-channel approach with atomic-like Dirac–Sturm–Fock orbitals, localized at the ions (atoms). The screening density-functional theory is applied for description of the interaction with passive electrons. The role of relativistic effects is analyzed.

Relativistic calculations of differential ionization probability in the U⁹¹⁺(1s)–U collision are performed in the monopole approximation. The method employs the active electron approximation, in which only the active electron of the H-like ion participates in the excitation and ionization processes while the passive electrons of the neutral atom provide a screening potential. The time-dependent Dirac wave function of the active electron is represented as a linear combination of the eigenstates of the unperturbed Hamiltonian localized at the H-like ion.

Recently, a new approach has been developed to treat the time-dependent two-centre Dirac equation within our group. This method generates basis wavefunctions describing an electron in the field of two nuclei at fixed internuclear distances in spherical co-ordinates, and uses coupled-channel techniques in handling the time dependences. Using this method, we analyse the electronic properties accompanying a U⁹²⁺–U⁹¹⁺ collision for a zero-impact parameter. Specifically, the ground state occupation probability and the ionization probability has been calculated. Based on our calculations, we show the importance of using higher multipole terms in the expansion of the two-centre potential.

A new approach for solving the time-dependent two-center Dirac equation is presented. The method is based on using the finite basis set of cubic Hermite splines on a two-dimensional lattice. The Dirac equation is treated in the rotating reference frame. The collision of U⁹²⁺ (as a projectile) and U⁹¹⁺ (as a target) is considered at energy E_lab = 6 MeV u⁻¹. The charge transfer probabilities are calculated for different values of the impact parameter. The results obtained are compared with previous calculations (Tupitsyn et al 2010 Phys. Rev. A 82 042701), where a method based on atomic-like Dirac–Sturm orbitals was employed. This work can provide a new tool for the investigation of quantum electrodynamics effects in heavy-ion collisions near the supercritical regime.

The characteristics of charge deposited (time) into a tapered glass capillary were studied for an incident energy of ∼ 1025 eV at a tilt angle of 5°. Electron beams resulting in intensities of 1.5–7000 nC deposited into a tapered borosilicate glass capillary were investigated for inlet/outlet diameters of 800/100 μm. The electron transmission consisted of stable transmission, fluctuations, blocking and self-discharging associated with a sudden rise of transmission as deposited charge was ejected from the capillary. In the case of stable transmission, it was found to be due to both elastic and inelastic contributions, with inelastic transmission dominant.

The transmission of 1 and 3 MeV protons through a borosilicate straight glass capillary and a tapered glass capillary was investigated. The straight capillary had a diameter of ∼0.18 mm and a length of ∼14.4 mm, while the tapered capillary had an inlet diameter of ∼0.71 mm, an outlet diameter of ∼0.10 mm and a length of ∼28 mm. The results show that the 1 and 3 MeV protons traverse through both samples without energy loss, while the tapered capillary showed better transmission than the straight capillary.

In order to establish in-air material analysis techniques with a glass capillary, we have measured energy distributions of extracted alpha particles in air using the glass capillary. We have estimated the effective air thickness in the glass capillary and found it to be compatible with a simple calculation.

The transmission of Xe¹⁰⁺ ions, with incident kinetic energies of 200–500 keV, through polycarbonate capillaries, with a diameter of 150 nm and a length of 30 μm, has been studied using a one-dimensional position sensitive detector. The transmitted ion yields were measured as a function of the tilt angle. The results are used to evaluate the guiding angle, which is a measure of the guiding power specifying the capability of insulating capillaries to guide ions at equilibrium. Following the semi-empirical scaling law, the potential in the entrance region in this work is nearly an order of magnitude larger than that proposed by low energy data.

We studied the anisotropy of Ly-α x-rays from H-like Ar¹⁷⁺ ions excited by polarization-controlled resonant coherent excitation. The effects of fine-structure depolarization on the 2p_1/2 and 2p_3/2 states were experimentally demonstrated as a reduction in anisotropy of decay radiation.

We have measured the ionization and fragmentation of polycyclic aromatic hydrocarbon (PAH) molecules and their clusters. We find that PAH clusters containing up to roughly 100 individual molecules fragment strongly following collisions with keV ions in low or high charge states (q). For both types of collisions, singly charged PAH molecules are found to be the dominant products but for very different reasons. A high-q ion projectile charge leads to strong multiple ionization of the PAH clusters and subsequent Coulomb explosions. A low-q ion projectile charge often leads to single ionization but stronger internal heating and long evaporation sequences with a singly charged PAH monomer as the end product. We have developed a Monte Carlo method for collision-induced heating of PAH clusters and present an evaporation model where the clusters cool slowly as most of the internal energies are stored in intramolecular vibrations and not in molecule–molecule vibrations.

The stability of multiply charged clusters of polycyclic aromatic hydrocarbons (PAHs) is theoretically investigated. We propose a new model (stacked structure model) for fragmentation of PAH clusters. The appearance size, a minimum cluster size such that the cluster remains stable when multiply ionized, is calculated by our new model as well as by the conventional liquid drop model. The appearance sizes for doubly charged clusters of anthracene and coronene calculated by the two models are found to be much smaller than those observed in the experiments. Possible reasons for the discrepancy are discussed.

We present a detailed study of the deformation of Au nanoparticles (NPs) caused by the irradiation of highly charged ions (HCIs). When spherical Au NPs with a diameter of 19.8 nm were irradiated by 1 MeV Xe²¹⁺ ions with a fluence of 2 × 10¹⁴ cm⁻², their anisotropic deformation was observed by atomic force microscopy. The results show that spherical Au NPs expand perpendicular to the ion beam changing their shape to oblate ellipsoidal. The size aspect ratio (major over minor axis) of the observed deformed Au NPs is about 1.23. The deformation process is described by a viscoelastic thermal spike model. The HCI beam deformation technique provides a unique method to tailor the shape of noble metal NPs.

We have recently demonstrated that individual slow highly charged ions are able to produce nano-sized pits on poly(methyl methacrylate) surfaces as a result of direct ablation due to the deposition of their high potential energy, if this energy exceeds a critical minimum value. By exposing irradiated samples to a suitable etchant, such pits can be revealed even below this potential energy threshold as latent damage zones are removed. Existing pits grow both in diameter and in depth after contact with the etchant with different etching dynamics for both dimensions. Systematic studies on the response of irradiated samples to a chemical developer are presented.

We have investigated the ionization of the H atom by half-cycle electric pulses in the framework of a pump–probe setup. Using this setup we have studied the holographic mapping (HM) of the target atom's state. Due to the simplicity and flexibility of the pump–probe approach, we were able to investigate in detail how the HM pattern is influenced by the electric field parameters.

We study Bessel beams of two-level atoms that are coupled to a linearly polarized laser field. For such atom beams, we construct exact Bessel-type solutions of the Schrödinger equation beyond the paraxial approximation for beam propagation. In particular, we examine the probability density for Bessel beams of neutral two-level atoms driven by a laser field but without the level damping being taken into account. We show how the radial dependence of the probability density (from the beam axis) can be affected by tuning the parameters of the atom–laser system, such as the resonant frequency and amplitude of the laser field and/or the nuclear charge and velocity of the atomic beam.

Recent experiments using highly charged ions (HCI) at Tokyo Metropolitan University and few cycle laser pulses at the advanced laser light source have centered on multiply ionizing carbonyl sulfide to form charge states from 3 +  to 7 + . By measuring the kinetic energy release during subsequent break up and comparing with previous results from HCI impact on CO₂ we can see a pattern emerging which implies that shorter laser pulses than the current sub 7 fs standard could lead to higher kinetic energy release than expected from Coulomb explosion.

Two-photon transitions in H- and He-like heavy ions in the presence of an external static electric field are explored using a relativistic Greens function approach and an independent particle model. The effects of Stark mixing on angular correlations, spectral distributions and total transition rates are analyzed in detail. Special emphasis is placed on the 2p_1/2 → 1s_1/2 two-photon transition in H-like ions and the 1s_1/22p_1/2:2³P₀ → 1s²_1/2:1¹S₀ and 1s_1/22s_1/2:2¹S₀ → 1s²_1/2:1¹S₀ two-photon transitions in He-like ions.

We report on a study of target-thickness effects on the degree of the linear polarization as well as on the emission probability of bremsstrahlung arising in the collision of 100 keV electrons with thin gold targets. For this purpose an experiment at the electron source SPIN at the TU Darmstadt as well as Monte Carlo simulations have been performed. The results indicate that for high-Z targets the degree of linear polarization is significantly altered by straggling of the electrons inside the target.

The effects of the spin–orbit interaction are pronounced for an electron scattered in a Coulomb field of the nucleus. They cause the electron scattering plane to turn or precess as the electron moves. This precession is visible through linear polarization of bremsstrahlung. The first experiment to observe it is described in this contribution.

The leading-order positron–atom bremsstrahlung is investigated within the rigorous relativistic approach based on the partial-wave representation of the Dirac wave functions in the external atomic field. Approximating the atomic target by an effective local potential, we calculate the Stokes parameters of the emitted photon for different polarizations of the initial positron. The results for positron–atom bremsstrahlung are compared with analogous data for the electron–atom bremsstrahlung.

The polarization correlations in the elastic scattering of spin-polarized electrons from unpolarized nuclei are compared with those which occur in the process of bremsstrahlung. The polarization correlations in these two reaction channels tend to agree for very heavy nuclei in the limit of ultrahigh collision energies.

A new experimental area for the investigation of ion beam matter interaction and ion beam plasma interaction was completed at the Institute of Modern Physics (Lanzhou, China). We report the details of this low-energy setup and first results on ion beam matter interaction, where we measured the charge state of O⁵⁺ ions at 1 MeV passing through a hydrogen gas target. The data were compared with the Monte-Carlo simulation results for cold hydrogen gas and hydrogen plasma.

We measured iron emission from the National Spherical Tokamak Experiment. We focused our attention on several band pass regions of the Solar Dynamics Observatory's Atmospheric Imaging Assembly. We found that all significant iron emission in the 171, 193 and 211 Å band pass regions are accounted for by the CHIANTI atomic database, although some strong emission lines of carbon are present that may complicate interpretation of solar data if not taken into account.

A specially designed pulsed discharge nozzle (PDN) ion source, a glow discharge pulsed supersonic jet, was constructed. The optical emission spectra of argon I and II in the region of 300–800 nm were observed and analyzed. The gas temperature of 3500 K and the ion one of 11 100 K were simulated by the Boltzmann plot method, and the electron density was simulated by Stark broadening of the H_α line. Owing to the big difference between the temperatures of Ar I and II, the plasma in the PDN is concluded to be in non-local thermodynamic equilibrium. The evolution of plasma parameters in the PDN was investigated also by using time-dependent emission spectra.

In this paper, we show that high-precision x-ray line measurements with a double-crystal spectrometer (DCS) on the plasma of an electron cyclotron resonance ion source can provide an experimental method for the determination of the natural line widths of the measured transitions. This goal can be achieved with full characterization of the response function of the used DCS with the help of a very narrow x-ray line in helium-like argon and a simulation code fully describing the geometry of the source and the DCS.

We have observed extreme ultraviolet spectra from highly charged gadolinium (Gd) and neodymium (Nd) ions produced in two different types of light sources for comparative studies. Only broad quasicontinuum feature arising from unresolved transition array was observed in high-density laser produced plasmas of pure/diluted Gd and Nd targets at the University College Dublin, and the spectral feature largely depends on electron temperature in optically thin plasmas produced in the Large Helical Device at the National Institute for Fusion Science. The difference in spectral feature among a number of spectra can be qualitatively interpreted by considering dominant ion stages and opacity effects in the plasmas.

The extreme ultraviolet emission spectra have been studied theoretically for gadolinium (Gd) and neodymium (Nd) atomic ions in the large helical device at National Institute for Fusion Science, Japan. The spectra have been analyzed and compared with the presently carried out atomic structure calculations using a group of computer codes GRASP92 and RATIP. The complex spectra from the unresolved transition array are generated theoretically. The theory has simulated well the experimental spectra.

Gradually stripping tungsten of its outer-shell electrons tends to increase the x-ray energies of the various Lα, Lβ and Lγ x-ray lines. For the Lα₁ and Lβ₁ lines the energy change is sometimes negative but always less than ≃10 eV when the ionization remains below W³⁰⁺; other lines increase their energy approximately quadratically with ionization level. Beyond W³⁰⁺ the increase is dramatic and some lines blue-shift many hundreds of eV already at W⁴⁰⁺. The computations are carried out with a multiconfiguration Dirac–Fock method that includes the Breit interaction and some QED corrections. The results are relevant to high-resolution x-ray diagnostics of plasma produced by short-pulse lasers and to some pulsed power plasmas.

Visible line emission from highly charged tungsten ions has been observed at the large helical device (LHD) using a tracer encapsulated solid pellet. One of the measured lines is assigned to a magnetic-dipole (M1) line of the ground-term fine-structure transition of W²⁶⁺. The other line is unidentified but probably due to a highly charged tungsten ion. Photon emission was observed at 40 lines of sight divided along the vertical direction of a horizontally elongated poloidal cross section of the LHD plasma. The line-integrated intensity of the M1 line along each line of sight indicates a peaked profile at the plasma center where the electron temperatures are high enough so that tungsten ions are highly ionized.

We present a review of measurements and analyses of extreme-ultraviolet magnetic-dipole (M1) lines in 50–60 times ionized atoms of tungsten, hafnium, tantalum and gold with an open 3d shell. The spectra were measured with the electron beam ion trap at the National Institute of Standards and Technology. Large-scale collisional–radiative modeling was instrumental in line identification and in analysis of their diagnostic potential. The M1 line ratios are shown to be an accurate and versatile tool for studying the LMN dielectronic resonances in 3dⁿ ions.

We present theoretical predictions for iridium Kα_1,2, Kβ_1,3 and Kβ₂ energy shifts as a function of outer-shell stripping, evaluated using the multiconfiguration Dirac–Fock method including Breit interaction and QED corrections. The energy shifts are consistent with the K-lines emitted by the plasma made in the plasma-filled rod pinch, and potentially relevant to diagnostics of high-energy density laser-produced plasmas as studied in connection with the National Ignition Facility.

The new international accelerator Facility for Antiproton and Ion Research (FAIR) which is currently under construction in Darmstadt has key features that offer a wide range of exciting new opportunities in the field of atomic physics and related fields. The facility will provide highest intensities of relativistic beams of both stable and unstable heavy nuclei, in combination with the strong electromagnetic fields generated by high-power lasers, thus allowing to widen atomic physics research into completely new domains. In the current contribution, a short overview of the SPARC (Stored Particle Atomic physics Research Collaboration) research programme at the FAIR facility is given. Furthermore, we present the current strategy for the realization of the envisioned SPARC physics programme at the modularized start version of the FAIR facility.

The physics program of the SPARC collaboration at the Facility for Antiproton and Ion Research (FAIR) focuses on the study of collision phenomena in strong and even extreme electromagnetic fields and on the fundamental interactions between electrons and heavy nuclei up to bare uranium. Here we give a short overview on the challenging physics opportunities of the high-energy storage ring at FAIR for future experiments with heavy-ion beams at relativistic energies with particular emphasis on the basic beam properties to be expected.

At the FAIR facility for antiprotons and ion research, the high-energy storage ring will provide highly charged heavy ions with Z all the way to Z = 92 for beam energies ranging from 200 A MeV up to energies of approximately 5 A GeV. This opens up a wealth of opportunities for in-ring atomic physics experiments on few-body quantum dynamics ranging from, for example, the correlated dynamics of various e⁺–e⁻ pair creation processes to quasi-photoionization of inner shells of the highest-Z ions.

At the FAIR facility for antiproton and ion research, the new ESR + CRYRING combination of storage rings CRYRING@ESR opens up a wealth of opportunities for in-ring atomic physics experiments on few-body quantum dynamics. The low-energy storage ring CRYRING will serve in its new location at FAIR/ESR for experiments with decelerated antiprotons and highly charged ions. We will discuss selected new experiments in the field of quantum dynamics of high-Z ions, for example for adiabatic superheavy quasi-molecules transiently formed with bare and H-like projectiles. Such experiments will be for the first time possible at the future CRYRING at ESR.

A resonant Schottky pickup was built into the experimental storage ring at GSI Darmstadt in 2010 and a similar one in the CSRe storage ring at IMP Lanzhou in 2011. Single-ion sensitivity was achieved at 400 MeV u⁻¹. The pickup has also been used in many storage ring experiments ever since. A brief description of the pickup and its application in single-ion lifetime spectroscopy is provided in this work.

By combining an x-ray laser (XRL) with a heavy-ion storage ring, precision laser spectroscopy of the fine-structure splitting in heavy Li-like ions will be possible. An initial study has been performed to determine the feasibility of a first experiment at the experimental storage ring at GSI in Darmstadt, which also has great potential for the experiments planned for FAIR. We plan to perform a unique, direct and precise measurement of a fine-structure transition in a heavy Li-like ion. Such a measurement will test state-of-the-art atomic structure calculations in strong fields. This endeavour will require that the existing infrastructure is complemented by a dedicated beamline for the XRL. In this paper, we will discuss the details of this project and outline a proof-of-principle experiment.

Laser cooling is one of the most promising techniques to reach high phase-space densities for relativistic heavy-ion beams. Preparations for laser cooling of relativistic lithium-like ions, such as C³⁺ and N⁴⁺, are being made at the experimental cooler storage ring (CSRe) in Lanzhou, China. In December 2011, a new buncher was installed and tested with a 70 MeV u⁻¹²²Ne¹⁰⁺ ion beam by electron cooling at the CSRe. The longitudinal momentum spread of the bunched ion beam was measured by the new resonant Schottky pick-up. As a result, Δp/p ≈ 2 × 10⁻⁵ has been reached at ion numbers less than 10⁷. According to this test result, the RF-buncher is suitable for the upcoming experiment of laser cooling at the CSRe. Laser cooling of heavy-ion beams will also be applied at future storage ring facilities, e.g. FAIR in Darmstadt, and HIAF in Lanzhou.

We have stored singly charged anthracene molecular ions C₁₄H₁₀⁺ in a compact electrostatic storage ring called the Miniring. The neutral yield curves due to dissociation of the ions induced by laser excitation at different storage times were analyzed and fitted with a t^−α law. The evolution of the internal energy distribution of the stored molecular ion ensemble was obtained as a function of the storage time by using a simple model which related the experimental decay factor α to the high-energy edge of the modeled energy distribution.

The Mini-Ring is a compact electrostatic ion storage ring designed for molecular relaxation dynamics studies. In order to accomplish an injection of the incoming ion beam, the electrode voltage settings appear to be quite critical to avoid large betatron oscillations. The beam injection was controlled by taking pictures of a test Ar⁺ ion beam with a digital camera. The amplitude of the betatron oscillation was measured by the impact position of neutral fragments exiting the ring on a position-sensitive detector. The broad spot observed for anthracene was attributed to the kinetic energy release resulting from the delayed unimolecular dissociation of anthracene by emission of a neutral C₂H₂.

For the investigation of electron–ion interaction processes, a new transverse electron target is under development. It opens the perspective to new types of experiments with ions by applying the 'crossed beam' technique for free electrons to a storage ring. The new target is suited for the UHV requirements of a storage ring and realizes an open geometry giving access to the interaction region for photon and electron spectroscopy under large solid angles. It is based on a simple design using only electrostatic fields for the focus of the sheet beam. The adjustable electron energy ranges between several tens of eV and a few keV. The electron target is dedicated to the storage rings of the Facility for Antiproton and Ion Research. First measurements are planned at a test bench, and subsequent tests at the Frankfurt Low Energy Storage Ring are envisaged.

In the framework of two master theses, the installation of a transverse electron target [1] in the Frankfurt low energy storage ring (FLSR) [2] is being prepared. A special type of electron beam ion source (EBIS) is being designed and will be built and tested. Usually in an EBIS a magnetic field is used for the radial trapping and the compression of the electron beam. The electron beam in a cross over (X)-EBIS is electrostatically focused to a crossover point, with no magnetic field employed. This property has a notable effect on the reduction of the dimension of the source, compared to a regular EBIS. The XEBIS will be commissioned in a test vacuum vessel, where the highly charged ions can be guided towards the transverse electron target and can be used for commissioning of the target prior to the test in the FLSR. In order to prepare the operation and tests of the transverse target in the FLSR, the beam dynamics of the ions in the ring has to be investigated with respect to the space charge effects of the electron beam of the target. Hence the focusing effect of the space charge derived from the target electron beam on the circulating ions is studied in detail. The goal is to determine the required tune change of the ring.

HITRAP is a facility at GSI in Darmstadt for decelerating, cooling and storing heavy, highly charged ions. It is designed to decelerate a beam of A/q < 3 particles with an energy of 4 MeV per nucleon as provided by the heavy ion storage ring ESR. HITRAP's decelerating linear accelerator (linac) will decelerate ions down to 6 keV per nucleon and then inject them into a Penning trap for cooling. The trap will capture bunches of up to 10⁵ ions as heavy as U⁹²⁺ in flight, cool and store them. After extraction from the cooler trap, the vertical beam line (VBL) transports the cold ions to the experiments. The linac has shown to decelerate ions down to 500 keV per nucleon on-line and to 6 keV per nucleon off-line. Recent tests with electrons and ions injected into the trap showed the necessity of a more careful electric and magnetic field alignment. An installed test ion source as well as a system of apertures and position sensitive diagnostics will be used to align the fields. A highly charged ion beam from a small room temperature electron beam ion trap was used for commissioning the VBL.

We present the status of the SpecTrap experiment currently being commissioned in the framework of the HITRAP project at GSI, Darmstadt, Germany. SpecTrap is a cryogenic Penning trap experiment dedicated to high-accuracy laser spectroscopy of highly charged ions (HCI) near rest. Determination of fine structure and hyperfine structure splittings in HCI with an expected relative spectral resolution of 10⁻⁷ will offer the possibility to test quantum electrodynamics in strong fields with unprecedented accuracy. Recently, we have demonstrated trapping and laser Doppler cooling of singly charged magnesium ions in SpecTrap. We report on the status of the experimental apparatus, measurements and present the future program toward storage and cooling of HCI.

At TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN), masses of short-lived nuclides are measured accurately and precisely using Penning trap mass spectrometry. The achievable precision is primarily limited by the radioactive lifetime of the nuclides. To boost the precision TITAN has demonstrated that short-lived isotopes can be charge-bred to higher charge states within 10–100 s of ms using an electron beam ion trap. The charge breeding process increases the energy spread of the ions, which in turn affects the precision and the efficiency. A novel cooler Penning trap (CPET) has been developed to trap and cool highly-charged ions using electrons prior to the precision measurement. A discussion of electron cooling and the current status of CPET will be given.

Ion charge breeding for Penning-trap mass spectrometry has been established as providing a precision increase that scales linearly with the charge state of the ion. Fast and efficient charge breeding is a precondition for the application of this approach to rare isotopes. However, in view of low yields and short half-lives the precision boost is partly compromised by unavoidable ion losses inherent to the charge breeding process. The mass spectrometer TRIUMFs ion trap for atomic and nuclear science is pioneering this field by coupling a Penning trap and an electron beam ion trap to the rare-isotope beam facility ISAC at TRIUMF. Here we present simulations that calculate and maximize the effective precision gain of time-of-flight ion-cyclotron-resonance measurements with highly charged ions of short-lived nuclides. In addition we compare the characteristics of measurements with singly and highly charged ions, and we summarize recent results that explored benefits of charge breeding that go beyond the precision increase.

The former Berlin electron-beam ion trap (EBIT) was moved to Greifswald. In addition to x-ray studies the setup will be used for the investigation of interaction processes between highly charged ions and atomic clusters such as charge exchange and fragmentation. The EBIT setup has now been reassembled and highly charged ions have been produced from Xe–Ar gas mixtures to study the 'sawtooth effect'. In addition, the layout of the extraction beamline, the interaction region and product analysis for interaction studies with highly charged ions are presented.

The ray tracing simulations of x-ray spectra for a compact six-crystal Johann/Johansson diffraction spectrometer covering a wide photon energy range (70 eV–15 keV), i.e. from the extended ultraviolet to the hard x-ray region, are discussed in the context of x-ray experiments at an electron beam ion source facility. In particular, the x-ray line profiles and energy resolution for different diffraction crystals and multilayers were studied, and the effects of extension of x-ray source size and misalignment were investigated. The simulations were also performed for x-ray emission from solid targets bombarded by electrons, which will be used for calibration of the x-ray spectrometer.

In this work, the digital readout of semiconductor detectors in combination with digital filters was investigated. Both non-segmented high-purity germanium and segmented planar lithium-drifted silicon detectors were used. In each case, photons from a stationary americium (²⁴¹Am) gamma source were detected. The resulting preamplifier output pulses were digitized at a fixed sampling frequency and stored entirely. Digital filters were applied to the stored waveforms to extract time and energy information. The performance of different digital filters was compared. The optimum energy resolution obtained was comparable with the value resulting from an analogue readout system based on standard nuclear instrumentation module and versatile module Europe bus electronics.

The future x-ray spectroscopy and polarimetry experiment program of the SPARC collaboration at GSI and FAIR relies strongly on the availability of two-dimensional position-sensitive, energy- and time-dispersive thick semiconductor detector systems, including the appropriate signal processing electronics. To meet these demands, the development of a compact and scalable data acquisition system that has higher rate acceptance compared to commercial VME electronics by employing digital pulse processing electronics was started.

We present a recently constructed double-crystal spectrometer with the purpose of measuring line energies of inner-shell transitions in highly charged ions. Due to its geometrical features, this spectrometer enables absolute measurements of energies with an unprecedented accuracy. We have also developed an ab initio simulation code that allows us to obtain accurate line profiles and estimate geometric and diffraction profile uncertainties. We show the first proof-of-principle measurements on highly charged ions done with this spectrometer. In particular, we present the recent measurement of the M1 transition in He-like Ar with an accuracy of 2.5 ppm and compare it with results of quantum electro dynamic theory.

In 2009 industry announced that sources would be needed at 6.x nm for future lithography. The brightest sources in this wavelength region are plasmas containing gadolinium and terbium. The strongest lines result from 4d–4f lines in the spectra of Ag-like Gd XVIII and Tb XIX through Rh-like Gd XX and Tb XXI. Assuming collisional radiative equilibrium, the optimum plasma temperature for producing these species is expected to be in the range 100–130 eV. Time integrated experimental spectra have been recorded with a variety of lasers and a maximum measured conversion efficiency (CE) for 150 ps pulses was 0.4%. The extreme ultraviolet (EUV) emission was observed to be anisotropic while the ion energy decreases with decreasing pulse length. The optimum laser intensity for efficient 6.7 nm EUV emission was determined to be close to 7 × 10¹³ W cm⁻², which gives an electron temperature of  ∼ 130 eV. The use of prepulses increases the CE which is limited by plasma opacity. To improve radiation transport low initial density targets and/or low electron density plasmas such as CO₂ LPPs are required.