Search

Sharp resonant structures in the cross section of the atomic electron-ion collision process of dielectronic recombination are exploited to study isotope shifts and hyperfine interaction of heavy highly-charged ions. This novel approach provides a conceptual alternative to existing methods. In this contribution, we present a series of measurements, which we performed at the heavy ion storage ring ESR of the GSI Helmholtzzentrum fur Schwerionenforschung, Darmstadt, Germany. In a first experiment the stable isotopes A = 142 and A = 150 of three-electron neodymium ANd57 + were studied. Isotope shifts of dielectronic resonances associated with 2s − 2pj (j = 1/2, 3/2) transitions were extracted from the measured data. The evaluation of the energy shift was performed within a full QED framework and yielded a change in the mean-square charge radius of \(^{142,150}\delta \langle r^2 \rangle = -1.36(1)(3)\) fm2. At GSI, in addition to the investigation of stable isotopes unstable species can be artificially synthesized and studied. Radioisotopes produced in-flight from fragmentation of a 238U primary beam were injected into the ESR and were subsequently separated by their mass-to-charge ratio. This enabled us to perform first DR experiments with the exotic nuclei 237U89 + (Z = 92 )and 234Pa88 + (Z = 91).

The use of targeted ion beams has been an important development for understanding the response of biological systems to radiation exposure. Most investigations in this field have been performed with helium ion microbeams; however, irradiations using a beam of protons, covering different LET values, can deliver complementary results and additional information on radiation effect related to radiation quality and low dose exposure. Recently, several experiments have been carried out at the new single ion hit facility in the Institute of Nuclear Physics in Cracow using a focused proton microbeam. In parallel, similar cross-validation experiments have been performed using the well-established particle microbeam situated at the Gray Cancer Institute with the same cell line and proton energy. Pilot studies have compared the yields of double strand breaks (DSBs) in cells uniformly irradiated with 240 kV X-ray with those irradiated with microbeam delivered protons, and in some cases helium ions. The number of DSBs increased with the X-ray dose. In the samples irradiated with individually counted protons, fewer foci were found in comparison to the number of protons delivered per cell. Studies also compared the distribution of foci per cell between the different radiation qualities.

Nanocrystalline titanium dioxide (nanoTiO2) has been reported to generate reactive oxygen species (ROS) under UV illumination. In our studies, changes in mechanical properties of human skin fibroblasts, exposed to the oxidative stress induced in the presence of nanoTiO2 and UV light, were studied using atomic force microscopy (AFM). The exposure of cells to the action of ROS was performed at low TiO2 concentration (4 microg/mL) and under illumination with low-intensity UVA (8 and 20 mW/cm2) or UVC (0.1 mW/ cm2). AFM measurements of the cell stiffness were carried out immediately after exposure of cells to the oxidative stress. The data suggest that under illumination with low-intensity UVA nanoTiO2 generates ROS, which, in turn, damage cellular and subcellular structures. This process was detected by AFM as a marked drop in the cellular stiffness of ca. 30-75%, which occurred rapidly, in the time frame of 1 min. The photo-oxidative stress inducing the decrease of cell stiffness was cancelled in the presence of a well-established antioxidant, beta-carotene. The results highlight the sensitivity of AFM to detect early changes in mechanical properties of cells exposed to oxidative stress.

Be-like ions have been investigated employing the resonant electron–ion collision process of dielectronic recombination (DR) as a spectroscopic tool. The experiments were performed at the experimental storage ring in Darmstadt, Germany, using its electron cooler as a target for free electrons. DR Rydberg resonance series for the associated intra-L-shell transitions and were observed with high resolution. In addition to these excitations from the ground state we determined resonances associated with excitations of ions initially in the metastable state. The corresponding excitation energies were determined to be and and . These excitation energies are compared with previous measurements and with recent state-of-the-art atomic structure calculations.

In this report we show first results on dielectronic recombination (DR) measurements with H-like uranium U 91 + . The experiments were conducted at the heavy ion storage ring ESR of GSI. The electron cooler of the ESR was used as a target for free electrons. Stochastic pre-cooling of the stored ion beam was employed in order to accomplish high-energy resolution at the necessary high electron–ion collision energies of more than 64 keV. For the DR of U 91 + this novel technique enabled us to measure for the first time the KLL-DR process and even to resolve the individual j – j ′ fine structure components of the KL j L j ′ resonances. The experimental data are compared with fully relativistic Multi-Configuration Dirac-Fock (DR-MCDF) calculations.

The Cracow single ion hit facility (SIH) is using the Van de Graaff-based microprobe with current spatial resolution of about 10 μm in vacuum. Living cells are irradiated with the exact number of 2 MeV protons. This work shows the present setup and test measurements optimizing the detection of single protons, beam deflection after registering single proton and the accuracy of cell targeting as well as the description of performance of the whole setup. The article presents also ways of cells visualisation and positioning during a single measurement and reports on first experiments with living cells carried out at the new facility.

The X-ray spectra produced by K-shell ionization in collisions of Li-like (U89+) uranium ions at an energy of 397 MeV/u with gaseous N2 target have been measured. The very high level selectivity during such collision has been found. The effect allows us to measure undistorted two-photon energy distribution from a decay of the 1s2s1S0 state in He-like uranium.

The lifetime of the 2 3P0 state in He-like uranium has been measured in a beam-foil time-of-flight experiment at the Gesellschaft fur Schwerionenforschung accelerator facility with the result τ(2 3P0) = 58.2(9.5) ps. With the measured lifetime it is possible to derive a value of Δ E 2 s Lamb = 76 . 3 ± 20 . 6 eV for the n = 2 Lamb shift in uranium.

Single ion bombardment of biological cells using an ion microprobe is a promising technique. However, for microprobe investigations of biological processes at a cellular level the precise recognition of a single cell and particularly of its nucleus is required. Moreover, cells must be examined in their natural state and environment (i.e. without previously being killed, preferentially not fixed nor stained) and, also, the use of ultraviolet light for cells observation should be avoided. Additionally, in order to obtain statistically significant results of irradiation, the possibility of fast automatic recognition of thousands of objects must be provided. Because computer recognition strongly depends on the quality of an image, the optical imaging system is of crucial importance. For this purpose one of the best solutions could be the Quantitative Phase microscopy (QPm) technique. QPm is the recent digital technique of phase contrast microscopy, providing quantitative phase and intensity data obtained from a series of defocused images. The following phase contrast modalities may be generated digitally from the computed QPm phase data with a greater degree of flexibility: Pure phase images (intensity-free), standard phase contrast (e.g. Zernike phase contrast), differential interference contrast (DIC), Hoffman modulation contrast, and simulated darkfield.

The Cracow microprobe was applied to determine the age of small detritalmonazite crystals extracted from the uppermost carboniferous sandstone of Upper Silesia Coal Basin (southern Poland). The method applied follows the technique of chemical dating of U–Th minerals: assuming that the monazite crystal is a closed system and all Pb within grain is radiogenic, it is possible to determine the age of a specimen by solving an equilibrium equation which includes as computational factors the elemental contents of U, Th and Pb and decay times of uranium and thorium. Using this approach, thanks to rather fast Pb accumulation in a crystal, monazite older than 100 My may be dated with relative ease. The investigated specimens were clusters of crystals, 30–100 μm in size, polished and mounted in Epoxy resin. Due to different geological history, the age of individual crystals from one sample may differ significantly, therefore the application of a microprobe has been necessary to extract information concerning single monazite grains. Two age groups were identified: small cluster, connected with Cadomian tectonothermal event (579±30 My) and dominating cluster, connected with Variscan tectonothermal event (329±19 My, 353±41 My). After successful preliminary measurements carried out in a provisory experimental chamber, an optimized chamber was constructed and set into operation for regular studies. Together with results of these investigations, the constructional details of the new chamber are presented.

Here we report on X-ray spectra induced by spontaneous capture of free electrons into decelerated bare- and hydrogen-like uranium ions which we measured recently at the cooler section of the ESR storage ring. The most intense lines observed in spectra can be attributed to direct transition of electrons into the K shell of the projectile ions and to characteristic L → K (Lyα) transitions. Radiative recombination lines into the K shell of bare and H-like uranium can be exploited for measuring the two-electron contribution to the ground state binding energy in helium-like uranium. The goal is to probe for high-Z ions bound-state QED corrections which are of the order of α2. Besides the dominant characteristic L → K transitions, the strongly reduced Bremsstrahlung (due to the low cooler voltage applied to the decelerated ions) allowed us to observe for the very first time RR transitions into the L shell as well as the balmer radiation located at the low-energy part of the spectra.

The KαL1 satellite spectrum of 29Cu was measured with a 5 inch Johansson crystal spectrometer after 2 MeV proton impact. The satellite spectrum was simulated by using Voigt profiles with a Lorentzian width which is obtained from the multiconfiguration Dirac–Fock (MCDF) calculations and convoluted with the Gaussian instrumental response function. A unique assignment of the strongest satellite transitions to visible structures in the experimental spectrum was based on a comparison of the predicted linear polarization of the transitions (using in calculations the intermediate coupling scheme) to their measured values. The simulated spectrum of the satellite transitions was fitted to the experiment. The fitted values of energies and relative intensities of the transitions are close to those obtained from the MCDF calculations. The alignment of the (1s2p)−2 double-vacancy state obtained from the measured polarization of the satellite spectrum is given by 20(1P 1) = −0.77(21) and 20 (3P) = −0.53(10) (values are not corrected for the Coster–Kronig transition). This is in agreement with the value reported for the KαL1 peak of Al.

Organometals are known to cause lysis of cells, but the molecular mechanism of their action is not recognized. In this work, we have examined the interaction of triphenyltin with erythrocyte membranes. We determined the order of haemolytic activity of the investigated organometal species as being: triphenyllead > tripropyltin = triphenyltin > triethyllead > trimethyltin. Such an order suggests that the haemolytic activity increases with the increasing hydrophobicity of the organic ligands. Compounds containing lead are more toxic than the respective complexes of tin. Triphenyltin chloride (Ph3SnCl) is very effective in lysis of erythrocytes. Using 119Sn Mossbauer spectroscopy we showed that triphenyltin interacts with the protein components of pig erythrocyte membranes in a highly specific way, but we did not detect any interaction of triphenyltin with pig haemoglobin. The Mossbauer spectrum was fitted with a single doublet characterized by hyperfine parameters that differ considerably from those reported for other organotin compounds in membranes of red blood cells. Applying the point charge model of the electric field gradient for the analysis of the environment of tin bonds from the quadrupole splitting, we could indicate Nhet from histidine and/or Sthiol from cysteine as the only possible ligands of Ph3Sn(IV). We expect that protein components of erythrocyte membranes having similar cysteine and histidine arrangement, such as in cat or rat haemoglobins, which provide high-affinity binding sites for organotins, can bind triphenyltin with high affinity. We give some arguments that ankyrin and β-spectrin are the most probable targets of Ph3Sn(IV) action and indicate its potential binding sites within the proteins. The highly specific interaction of triphenyltin with the membrane cytoskeleton components, postulated by us, should already influence the rigidity of red blood cells at the stage preceding the lysis of erythrocytes. To support this hypothesis, we carried out scanning force microscopy measurements of red blood cells elasticity. We have observed a lower stiffness for erythrocytes treated with concentrations of Ph3SnCl that caused less than 20% of haemolysis. Copyright © 2002 John Wiley & Sons, Ltd.

A new scanning nuclear microprobe (MP) with a short-length probe forming system has been designed and installed at the 3 MV van de Graaff accelerator in Cracow. The optimized probe forming system (PFS) includes a divided Russian quadruplet of magnetic quadrupole lenses. A novel beam scanning system with ferrite-cored magnetic coils is used. Preliminary experimental results and some features of the MP are described. The design developed is promising for the next generation of compact and vertical nuclear MPs.

The paper describes an optimized scanning nuclear microprobe (MP) with a new ultra-short (total length of 1.85 m) probe forming system based on a divided Russian quadruplet (DRQ) of magnetic quadrupole lenses. Modern electrostatic accelerators have a comparatively high beam brightness of about 10–25 pA/μm 2 /mrad 2 /MeV. This allows the MP proposed to provide a high lateral resolution even with large (1%) parasitic (sextupole and octupole) pole tip field components in all lenses. The features of the design permit the MP operation in the high current and low current modes with a short working distance and inexpensive quadrupole lenses. A new quadrupole doublet design has been developed for the MP. In the present work the calculated features of the new MP are compared with preliminary experimental results obtained with a similar system (total length of 2.3 m) at the INP in Cracow. The new MP is promising for studies of solids or biological samples with high resolutions (0.08–2 μm) in both modes under ambient conditions. A vertical version of the ultra-short MP can be very useful for single ion bombardments of living cells.

Strong evidence has been found for enhanced multiple electron capture into 46 MeV/u Pb81+ with a significant contribution from the entrance surface of thin carbon foils. Capture of up to five electrons has been observed. The multiple electron capture yield is found to increase with decreasing target thickness for thin targets. A simple model describing the data and showing the importance of capture from surfaces is discussed. Further evidence is found for a pronounced asymmetry between electron capture at the entrance and the exit surfaces. Absolute yields for multiple electron capture and projectile ionization are presented. The experimental total cross sections for single capture and ionization agree well with theory.

A new nuclear microprobe has been constructed at the Van de Graaff accelerator (HVEC, KN-3000) in the Institute of Nuclear Physics in Cracow. The focusing system is based on two doublets of magnetic quadrupole lenses forming a “Divided Russian Quadruplet” geometry. Numerical calculations of the ion optics are published elsewhere [V. Brazhnik, S. Lebed, W. Kwiatek, Z. Stachura, M. Cholewa, D. Jamieson, G. Legge, Nucl. Instr. and Meth. B 130 (1997) 104]. In the present work details of the design are shown and the first experimental results are compared with the theoretical expectations. The advantage of the described construction is a short total length of the microprobe of 230 cm. A so short microprobe may be very convenient in some application to biophysics where a vertical position of the beam line is preferable. Also, because of the short length of the system, spherical and chromatic aberrations only slightly influence the final resolution of the microprobe.

Scanning force microscopy (SFM) can be used in nano-indentation experiments for very soft samples of elastic, organic materials. The present paper describes the methodology of device calibration and Young's moduli determination, to evaluate the elastic properties of living cells in their culture conditions. Two similar lines of normal cells (Hu609) and cancerous ones (T24) were measured. A significant difference in Young's modulus for normal and cancerous cells was detected.

In a first pilot experiment the absorption-edge spectroscopy was applied at the gas-jet target of the ESR storage ring in order to measure the ground state transitions of H- and He-like gold-ions. The aim of this experiment was to test the potential of this technique for a precise study of QED-effects in high Z ions at the storage ring.

The bremsstrahlung process in the domain of strong Coulomb fields has been investigated for and Ar target electrons colliding with He-like uranium ions at . The differential cross sections for bremsstrahlung were measured at laboratory observation angles of , , and . Substantial discrepancies were found between the experimental cross sections and the first-order Born approximation calculations. The reported data provide a new testing ground for non-perturbative treatment of the coupling between radiation and matter in the presence of strong fields.

The study of projectile excitation of high-Z ions in collisions with light target atoms is a powerful tool for the investigation of magnetic and higher-order effects occurring in relativistic collisions. Very first investigations performed for bismuth ions were recently extended at the ESR storage ring by using He-like uranium ions in collisions with gaseous targets. At the ESR jet target, the absence of solid-state effects (e.g., multiple collisions) allows one to study higher order processes, such as excitation and ionization or excitation and capture, occurring in single collisions.

Dielectronic recombination (DR) and radiative recombination (RR) of lithium-like gold in the energy range of 0 to 225 eV have been studied at the Experimental Storage Ring (ESR) of the GSI in Darmstadt. Main objective of the measurements is the precise determination of the 2s1/2−2p1/2 energy splitting as an additional QED test. This novel method, developed at the ESR [1], is based on the extrapolation of a multitude of measured resonances Au75+ (1s22p1/2nlj) up to the series limit (n = ∞). Furthermore experimental data for the Au75+ (1s22p3/26lj) resonance manifold are presented.

K-shell ionization and excitation is studied for high-Z one-and two-electron ions in relativistic encounters with low-Z targets. For ionization, the data obtained for solid and gaseous targets are compared in detail with the predictions of first order perturbation theory. On the basis of the most recent experimental results, the systematic deviation from first order perturbation theory as observed recently for high-Z ions cannot be confirmed. Moreover, special emphasis is given to a dedicated experiment where projectile excitation has been studied in encounters of heavy one-and two-electron bismuth ions (Z = 83) with light solid targets. The measurement of the characteristic ground-state transitions in coincidence with the primary charge state allowed us to study the formation of excited projectile states via direct Coulomb excitation. In particular, due to the large fine-structure splitting, the excitation cross-sections for the various L-shell sublevels in H- and He-like bismuth could be determined separately. The results are compared with detailed relativistic calculations showing that for high-Z projectiles the magnetic interaction is of considerable importance at the considered collision energies.

The deceleration capabilities of the ESR have been used for the first time in a dedicated ground state QED experiment conducted at the gasjet target of the ring. By decelerating bare uranium ions from 358 MeV/u down to energies of as low as 49 MeV/u, X-ray spectra have been obtained which provide an abundant yield of characteristic X-ray transitions. The experiment demonstrates that, by choosing the appropriate beam energy and gasjet target, almost all excited projectile states can be selectively populated. Moreover, the experiment provides the first data for beam lifetimes of stored decelerated high-Z ions. Such data are essential for the design of future experiments dealing with decelerated ion beams far below 50 MeV/u.

We have performed a measurement of the spectral shape from the two-photon decay of the $1s2s{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ state in He-like uranium. The two-photon emission followed the ionization of initially Li-like uranium ions in collisions with a N${}_{2}$ gas-jet target. The measured shape of the two-photon energy distribution shows good agreement with results of the relativistic calculations that take into account the electron-electron interaction rigorously up to the first order in quantum electrodynamic perturbation expansion. From the full width at half maximum of the measured two-photon energy distribution, we confirm the theoretically predicted modification of the shape due to the relativistic effects.

Scanning force microscope has been applied to investigate wear tracks produced during friction coefficient measurements of hard steel ball against (111) silicon crystals implanted with Ar ions. Such treatment causes the stable and significant decrease in friction, despite the total removal of implanted species from the wear track during friction. Scanning force microscope measurements of wear tracks topography supported the former hypothesis assuming the formation of post-implantation dense microcracks structure and subsequent propagation of this structure into the bulk. Such process assures small size of wear particles and a low friction coefficient value. Additionally the microfriction force measurement method was applied to determine the friction coefficient of Si3 N4 cantilever and a wear track in Si crystal.

Resonant transfer and excitation in highly charged uranium ions has been investigated by applying the X-ray/particle coincidence technique. This complete detection method for the RTE process in combination with the large L-shell fine structure splitting in uranium allows, for the first time, an L-subshell differential as well as angular differential study of the excitation and radiative stabilization of different intermediate electronic states. Measured L-subshell differential cross sections for the KLL-RTE in U 90+ →C collisions compare well with full relativistic calculations. For the radiative stabilization of the KL 1 2 L 3 2 intermediate states a significant anisotropy was found.

By decelerating highly-charged, very heavy ions to low energies in the storage and cooler ring, ESR, a new brilliant source for projectile x-rays has been obtained. In a first precision spectroscopy experiment up to 2·107 stored bare U92+ ions have been decelerated down to 49 MeV/u before detecting the characteristic projectile x-rays associated with one-electron capture at the ESR gas target. The Lyman, Balmer and Paschen series are distinctly observed for hydrogenic U91+ ions.

Resonant transfer and excitation (RTE) followed by X-ray emission in highly charged uranium ions colliding with carbon atoms has been investigated by applying the X-ray-particle-coincidence technique. This renders possible a subshell differential investigation of the population and radiative stabilization of different excited intermediate states. Preliminary results for the measured RTE excitation function for U 90+ → C collisions are presented.

Measurements of the photon angular distribution of Radiative Electron Capture into the M shell have been performed with He-like uranium ions in the range 110–140 MeV/u. In addition, L REC was studied at a projectile energy of 140 MeV/u. In both cases, the experimental data show an asymmetry around 90° and agree well with a fully relativistic theory.

The aim of this research was to find out whether the passage number effect may influence on the PC-3 cells (the human prostate cancer line derived from bone metastases) response to proton radia- tion. 2 MeV horizontally focused proton microbeam was used as a radiation source. The cells were treated with a counted number of H + ions (50-8000) corresponding to doses of 1.3-209 Gy/cell. For comparison, cell death was also induced by UVC radiation. All cells were stained with Hoechst 33342 and propidium iodide and visualized under a fluorescence microscope. Necrosis was observed at: a) 8000 protonsper cell (corresponding to ~209 Gy/cell) after 2-4 passages, b) 3200 protons per cell (corresponding to ~84 Gy/cell) for cells after 11-14 passages and c) only 800 protons per cell (corresponding to ~2 Gy/cell ) after 47-50 passages. Apoptosis was efficiently induced, by protons, only in cells after 50 passages. The results showed that the laboratory conditions affected cellular response of PC-3 cell line to the proton irradiation. The cellular response to the radiation treatment strongly depends on number of passages.

Projectile X-ray emission and charge-exchange processes are studied for bare and one-electron Bi, Pb, and U ions in collisions with gaseous and solid targets at relativistic energies. The experimental data for both the total and subshell differential cross sections are discussed and compared with theoretical predictions. Moreover, the experiments were extended to atomic structure studies. The result for the groundstate Lamb-shift for hydrogenic uranium is presented, which compares very well with theoretical prediction.

The expression of N-cadherin, characteristic of various cancers, very often leads to changes in the cells' adhesive properties. Thus, we sought to find out if N-cadherin expressed in various, but cancer-related cells, differs in its functional properties that could contribute to variations in cells' phenotypes. In our work, measurements of an unbinding force of a single N-cadherin molecule, probed with the same antibody both on a surface of living non-malignant (HCV29) and malignant cells (T24) of bladder cancer, were carried out with the use of an atomic force microscopy. The results show the enhanced N-cadherin level in T24 malignant cells (8.7% vs. 3.6% obtained for non-malignant one), confirmed by the Western blot and the immunohistochemical staining. The effect was accompanied by changes in unbinding properties of an individual N-cadherin molecule. Lower unbinding force values (26.1 ± 7.1 pN) in non-malignant cells reveal less stable N-cadherin complexes, as compared to malignant cells (61.7 ± 14.6 pN). This suggests the cancer-related changes in a structure of the binding site of the antibody, located at the extracellular domain of N-cadherin. Copyright © 2011 John Wiley & Sons, Ltd.

Absolute rate coefficients for dielectronic recombination (DR) of H-like ${\mathrm{U}}^{91+}$ ions have been measured. The electron-ion merged-beam technique at a heavy-ion storage ring was employed using a stochastically cooled ion beam. Thereby, the previously accessible electron-ion collision energies could be greatly extended to the range 63--90 keV. High-resolution DR spectra were measured covering all $\mathit{KLL}$ and $\mathit{KLM}$ resonances. For the resonance strengths, excellent agreement between relativistic theory and experiment is found only if the Breit contribution to the electron-electron interaction is included in the calculations. For the $\mathit{KL}$${}_{1/2}$$L$${}_{1/2}$ and $\mathit{KL}$${}_{1/2}$$M$${}_{1/2}$ groups the Breit contribution amounts to 44% of their total resonance strengths.

Radiative Electron Capture (REC) in 4 to 12 MeV/u Ge31+→H2 collisions has been studied using an X-ray/particle coincidence technique. This technique allowed a systematic investigation ofK-shell REC as well as a separation of REC into the projectileL- andM-shells. The cross sections are discussed within a general scaling picture based on the reduced projectile velocity.

The study of isotope shifts and hyperfine effects in dielectronic recombination (DR) resonance spectra strikes a conceptually new path for investigations of nuclear properties such as charge radius, spin, magnetic moment of nuclei or lifetimes of long-lived excited nuclear states. A series of DR experiments with heavy three-electron ions (Li-like) was performed at the heavy-ion storage ring ESR of the GSI Helmholtzzentrum fur Schwerionenforschung, Darmstadt, Germany. In a pilot experiment the two stable isotopes A=142 and A=150 of neodymium ANd57+ were investigated. From the displacement of DR resonances the isotope shifts δE142,150(2s – 2Pl/2) = 40.2(3)(6) meV and δE142,150(2s – 2p3/2) = 42.3(12)(20) meV for 2s – 2Pj transitions of the Li-like ions have been obtained. An evaluation within a full QED framework yielded a change in the mean-square charge radius of 142,150δ(r2) = −1.36(1)(3) fm2. At GSI, in addition to stable isotopes, in-flight synthesized radioisotopes can be studied as well. The production of radioisotopes of interest, the subsequent separation in the storage ring ESR and first DR experiments with the exotic nuclei 237U89+ and 234Pa88+ (Z=91) are presented. The paper is concluded with a brief outlook at future DR experiments with heavy radioisotopes at the ESR.

We report on the visualization of the penetration of sunscreen formulations containing TiO2 nanoparticles (about 20 nm primary particle size) into hair follicles of both human and porcine skin using the complementary methods of ion microscopy (PIXE, RBS, STIM) and autoradiography. Particles were found as deep as approx. 400 pin in the follicle, obviously introduced mechanically rather than by a diffusive process. No particles were observed in vital tissue nor in sebaceous glands. (c) 2007 Elsevier B.V. All rights reserved.

The determination of atomic lifetimes offers the possibility to investigate various aspects of the atomic structure. In the case of helium-like 197Au with nuclear spin 3/2, due to hyperfinequenching, one can determine the 23 P 0-23 P 1 fine-structure splitting from the lifetime measurement of the metastable 23 p 0 state. This lifetime has been measured at the GSI accelerator facility with the beam-foil time-of-flight technique and has taken advantage of particle-X-ray coincidences using a charge state spectrometer in conjuction with a newly developed CVD-diamond particle detector. A preliminary analysis has given a value of 22.45 ± 0.66 ps for the lifetime of the 23 P 0 state in helium-like gold. This is in good agreement with theoretical predictions.

The ESR storage ring offers unique conditions for precision investigations in the realm of atomic structure and collisions research at highest nuclear charges. For atomic structure studies, a very recent experiment will be discussed aiming on a precise determination of the electron-electron QED contribution to the groundstate ionization potential in He-like uranium. For the regime of collision dynamics, the close interplay between dynamics and atomic structure is outlined. Here, for the case of the 2p3/2 → 1s1/2 transition in H-like uranium, a strong interference between the El and M2 transition amplitudes has been identified which gives rise to a remarkable modification of the angular distribution of emitted photons.

Absolute yields for multiple electron capture as well as projectile ionization have been measured for 46 MeV/u U91+ ions traversing thin carbon foils with different surface topologies. Multiple electron capture yields vary strongly, depending on the target manufacturer. The samples including the one with the smoothest surface show a deviation of the yield from the expected scaling based on subsequent single capture for decreasing target thickness. This indicates a strong contribution of the surface, whose nature cannot be identified by the current data.

For He-like uranium, a state-selective electron-capture study was carried out for relativistic collisions with gaseous targets. In the experiment, the projectile x-ray emission produced by electron capture in collisions of 223-MeV/u ${\mathrm{U}}^{90+}$ ions on ${\mathrm{N}}_{2},$ Ar, Kr, and Xe targets was measured in coincidence with ${\mathrm{U}}^{89+}$ projectiles. Due to the large fine-structure splitting in heavy ions, the well-resolved Balmer transitions observed were used to deduce subshell sensitive cross sections for electron capture. For this purpose, a theoretical spectrum analysis and simulation was performed by taking into account electron cascades from states up to $n=40.$ The state-selective data are compared with theoretical calculations as a function of target atomic number. An overall agreement is found between the experimental data and the theoretical approaches applied except for the j-sensitive part.

Electron-ion recombination of completely stripped ${\mathrm{Bi}}^{83+}$ has been investigated at the Experimental Storage Ring (ESR) of the GSI in Darmstadt. Absolute recombination-rate coefficients have been measured for relative energies between ions and electrons from 0 up to about 125 eV. In the energy range from 15 meV to 125 eV, the experimental result is well described by the theory for radiative recombination (RR). However, below 15 meV the experimental rate increasingly exceeds the RR calculation by up to a factor of 5.2. This puzzling enhancement phenomenon, which has already been observed at other storage rings and single-pass merged-beams setups, is reported here from the ESR and for a bare ion heavier than argon. The enhancement is insensitive to changes of the electron density, which in subsequent measurements was set to $1.6\ifmmode\times\else\texttimes\fi{}{10}^{6},$ $3.2\ifmmode\times\else\texttimes\fi{}{10}^{6},$ and $4.7\ifmmode\times\else\texttimes\fi{}{10}^{6}{\mathrm{cm}}^{\ensuremath{-}3}.$ An additional variation of the magnetic guiding field of the electrons from 70 mT to 150 mT in steps of 1 mT resulted in oscillations with a period of 7.6 mT of the rate that are accompanied by considerable changes of the transverse electron temperature.

Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold.

The Lyman- $\ensuremath{\alpha}$ transitions of hydrogenlike uranium associated with electron capture were measured in collisions of stored bare $\mathrm{U}{}^{92+}$ ions with gaseous targets at the storage ring ESR. By applying the deceleration technique, the experiment was performed at slow collision energies in order to reduce the uncertainties associated with Doppler corrections. From the measured centroid energies, a ground state Lamb shift of $468\mathrm{eV}\ifmmode\pm\else\textpm\fi{}13\mathrm{eV}$ is deduced which gives the most precise test of quantum electrodynamics for a single electron system in the strong field regime. In particular, the technique applied paves the way towards the 1 eV precision regime.

Charge-exchange cross sections and beam lifetimes are studied for decelerated bare uranium ions at the ESR storage ring. By deceleration from the initial energy of 358 MeV/u down to various energies as low as 49 MeV/u, i.e., far below the production energy of bare ionic species, the electron pickup cross sections were obtained for collisions with ${\mathrm{N}}_{2}$, Ar, ${\mathrm{CH}}_{4},$ and Kr gaseous targets. The measured cross sections and beam lifetimes are compared with the theoretical results for radiative and nonradiative electron capture. The present data, along with the theoretical approximations discussed, provide a solid basis for the estimation of beam lifetimes for decelerated bare high-$Z$ ions. Moreover, a normalization procedure is proposed, in which absolute total charge-exchange cross sections are derived by normalizing the simultaneously measured yield of radiative electron capture photons to rigorously calculated relativistic cross sections. This method, along with the unprecedented beam conditions at the ESR storage ring, allows a significant improvement of the accuracy of cross-section data.

Absolute rate coefficients for dielectronic recombination (DR) of hydrogenlike U91+ have been measured at GSI's heavy-ion storage ring ESR in the center-of-mass energy range 63–90 keV. We find an excellent agreement between the measured DR rate coefficients and theoretical results from multi-configuration Dirac-Fock theory which includes the Breit interaction. The latter contributes nearly one half to the total resonance strengths of the KL1/2L1/2 and KL1/2M1/2 resonance groups.

Dielectronic recombination measurements with Li-like in-flight produced actinides were performed at the storage ring ESR of the GSI Helmholtzzentrum fur Schwerionenforschung employing the ring's cooler as a target for free electrons. The extension of the DR technique for the investigation of isotope effects towards shortlived nuclei (> 10 s) is a major advance and enables new types of experiments at the interface of atomic and nuclear physics.

Absolute rate coefficients for dielectronic recombination of Be-like Xe50+ have been measured by employing the electron-ion merged beam technique at GSI's heavy-ion storage ring ESR in the center-of-mass energy range 0 – 600 eV. In addition to ground state ions, resonances from metastable Xe50+ (2s2p3P0) parent ions have been observed. These may be exploited in future measurements of the E1M1 two photon 2s2p3P0 → 2s2 1S0 transition rate.