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Platinum nanoparticles have been synthesized on gas diffusion layers (GDLs) by means of electrochemical synthesis. Two types of GDLs were used (hydrophobic and hydrophilic) to study the effect of surface properties on the electrodeposition of Pt nanoparticles. Better coverage of Pt nanoparticles has been observed in the case of using a hydrophilic carbon GDL; nanoparticles with lower size were synthesized as well. Characterization of hydrogen evolution reaction by cyclic voltammetry showed a better performance of the electrodes synthesized by electrochemical methods when compared with commercial ones with an equal Pt loading (2 mg·cm-2)

[EN] Cerium-containing microcapsules were obtained by means of water/oil (W/O) emulsion technology using tetraethyl orthosilicate (TEOS) as the precursor. Synthesis parameters as water/ethanol molar ratio, surfactant concentration, temperature, synthesis time, were optimized to obtain microcapsules with adequate form and size. Cerium salt is a corrosion inhibitor. Scanning electron microscopy (SEM) was employed to characterize the microcapsules and EDS and energy dispersive X-ray (EDX) microanalysis to assess encapsulation of cerium. The synthesized microcapsules were incorporated in the sol-gel coating that was sprayed on AA2024 aluminum alloy. The morphology of the sol-gel coating and the distribution of the microcapsules were investigated by SEM and EDX and the corrosion resistance of the coated samples was evaluated by electrochemical impedance spectroscopy (EIS) and open circuit potential measurements. Cerium microcapsules can act as Ce nanoreservoirs blocking defects produced in the organic-inorganic hybrid coating by precipitating Ce oxide/ hydroxide and nanoloads slowing the diffusion of redox species to the aluminum surface. Higher corrosion resistance was obtained with microencapsulation of cerium than with nonencapsulated cerium., Authors wish to thank to the Instituto Valenciano de Competitividad Empresarial (IVACE) (project reference IMAMCC/2016/1) for the financial support. Electron Microscopy Service of the UPV (Universitat Politecnica de Valencia) is gratefully acknowledged for help with FESEM and EDX characterization.

International audience

A heavy-ion detector was developed for decay studies in the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. This detector serves as a prototype for the in-pocket particle detectors for future experiments with the Collector Ring (CR) at FAIR (Facility for Antiproton and Ion Research). The detector includes a stack of six silicon pad sensors, a double-sided silicon strip detector (DSSD), and a CsI(Tl) scintillation detector. It was used successfully in a recent experiment for the detection of the β+-decay of highly charged 142Pm60+ ions. Based on the Δ E / E technique for particle identification and an energy resolution of 0.9% for Δ E and 0.5% for E (Full Width at Half Maximum (FWHM)), the detector is well-suited to distinguish neighbouring isobars in the region of interest.

Isochronous mass spectrometry was applied to measure isomeric yield ratios of fragmentation reaction products. This approach is complementary to conventional gamma-ray spectroscopy in particular for measuring yield ratios for long-lived isomeric states. Isomeric yield ratios for the high-spin I = 19/2 states in the mirror nuclei 53Fe and 53Co are measured to study angular momentum population following the projectile fragmentation of 78Kr at energies of 480A MeV on a beryllium target. The 19/2 state isomeric ratios of 53Fe produced from different projectiles in the literature have also been extracted as a function of mass number difference between projectile and fragment (mass loss). The results are compared to ABRABLA07 model calculations. The isomeric ratios of 53Fe produced using different projectiles suggest that the theory underestimates not only the previously reported dependence on the spin but also the dependence on the mass loss., Comment: 6 pages, 5 figures

Masses of uranium fission fragments have been measured with the FRagment Separator (FRS) combined with the Experimental Storage Ring (ESR) at GSI. A 410-415 MeV/u 238U projectile beam was fast extracted from the synchrotron SIS-18 with an average intensity of 109/spill. The projectiles were focused on a 1g/cm2 beryllium target at the entrance of the FRS to create neutron-rich isotopes via abrasion-fission. The fission fragments were spatially separated with the FRS and injected into the isochronous storage ring ESR for fast mass measurements without applying cooling. The Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without B $\rho$ -tagging at the high-resolution dispersive central focal plane of the FRS. The evaluation has been done for the combined data sets from both experiments with a new method of data analysis. The use of a correlation matrix has provided experimental mass values for 23 different neutron-rich isotopes for the first time and 6 masses with improved values. The new masses were obtained for nuclides in the element range from Se to Ce. The applied analysis has given access even to rare isotopes detected with an intensity of a few atoms per week. The novel data analysis and systematic error determination are described and the results are compared with extrapolations of experimental values and theoretical models.

238U projectile fragments have been created at the entrance of the fragment separator FRS, spatially separated in flight within 0.45 μs and injected into the storage-cooler ring ESR at 7.9 Tm corresponding to about 70% light velocity. Accurate new mass values and lifetime information of the stored exotic nuclei in the element range from platinum to uranium have been obtained with single-particle Schottky spectrometry. In this experiment the new isotopes of 236Ac, 224At, 221Po, 222Po, and 213Tl were discovered. The isotopes were unambiguously identified and their masses measured. In addition, the time-correlated data have provided information on the lifetime of the new nuclides. The discovery of isotopes along with accurate mass measurement has been achieved for the first time at the FRS-ESR facility. The results will contribute to the knowledge of the decay products from the r-process nuclei and enable a crucial test of the predictive power of modern nuclear mass and half-life models.

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).

An analytical procedure is proposed for the independent quantitative chemical analysis of each element in the presence of other elements in the matrix of a sample by Energy Dispersive Electron Probe Microanalysis. For this purpose, an empirical calibration technique (which we shall call here the JABO method), which studies the variation of the X-ray intensities in terms of the analyte concentration in a chemical system with a complex matrix, is established. The methodology consists of the modification of the unknown sample by addition of a diluent, an internal standard and the analyte itself (dilution-addition method). A mathematical model is proposed to calculate the K parameters for the analyte ( K i ) and standard ( K p ) in each sample. A series of glass discs for each analyte are prepared which make it possible to obtain experimental values of characteristic X-ray lines. Some new K parameters are defined as K i and K p quotients, which remain constant in a wide concentration range. This allows us to use them for the calculation of the component concentrations of the unknown sample, as reproducing mathematical expressions between X-ray intensity and analyte concentration are obtained. An algorithm is proposed to calculate the component concentration in a sample with a complex matrix where components exist with a strong interelemental interaction effect. The method has been applied satisfactorily to the determination of titanium (accuracy 3%) and zinc (accuracy 0.5%) in the presence of a large proportion of zirconium which acts as interferent.

In this contribution, we present an experimental study carried out at GSI Darmstadt devoted to investigation of quantum electrodynamical (QED) effects for the ground states in hydrogen- and helium-like uranium. In the experiment, X-ray spectra following radiative recombination of free electrons with bare and H-like uranium ions (U92+, U91+) were measured at the electron cooler of the ESR storage ring. Utilizing clean and favorable experimental conditions present at the electron cooler, we were able to obtain very accurate values for the ground-state binding energies from the observed X-ray transitions. When compared with theory, our results provide the most stringent test of bound-state QED for one- and two-electron systems in the strong-field regime.

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.

An excited metastable nuclear state of 192Os in a hydrogen-like charge state has been studied for the first time. It was populated in projectile fragmentation of a of 197Au beam on a of 9Be target with the UNILAC-SIS accelerators at GSI. Fragmentation products in the region of interest were passed through the fragment separator and injected into the experimental storage ring (ESR). Cooling of the injected beam particles enabled Schottky mass spectrometry to be performed. Analysis shows the lifetime of the state to be considerably longer than that of the neutral ion [τneut=8.5(14)s]; this change is attributed to hindrance of internal conversion in hydrogen-like of 192Os. Calculations have been performed to estimate the lifetime, and the result has been compared with that measured experimentally. There is good agreement between the expected [τH−like=13.0(24)s] and measured lifetimes (τrest=15.1+1.5−1.3 s) from the internal decay of of 192mOs. This provides a test for the reliability of the values obtained from internal conversion coefficient calculations in highly ionized systems and is the first measurement of its kind to be performed using the ESR setup.

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.

CAS; International audience; In two experiments performed with 20-30 MeV/u highly charged heavy ions (Pb56+, U91+) channeled through thin silicon crystals, we observed the original features of superdensity, associated to the glancing collisions with atomic rows undergone by part of the incident projectiles. In particular the very high collision rate yields a quite specific charge exchange regime, that leads to a higher ionization probability than in random conditions. X-ray measurements show that electrons captured in outershells are prevented from being stabilized, which enhances the lifetime of the projectile innershell vacancies. The charge state distributions and the energy loss spectra are compared to Monte-Carlo simulations. These simulations confirm, extend and illustrate the qualitative analysis of the experimental results.

International audience; We report on the observation of a strong perturbation of the electron gas induced by 20 MeV/u U91+ ions and 13 MeV/u Pb81+ ions channeled in silicon crystals. This collective response (wake effect) induces a shift of the continuum energy level by more than 100 eV, which is observed by means of radiative electron capture into the K- and L-shells of the projectiles. We also observe an increase of the REC probability by 20–50% relative to the probability in a non-perturbed electron gas. The energy shift is in agreement with calculations using the linear response theory, whereas the local electron density enhancement is much smaller than predicted by the same model. This shows that, for the small values of the adiabaticity parameter achieved in our experiments, the density fluctuations are not strongly localized in the vicinity of the heavy ions.

A semi-empirical model has been developed to quantify the interelemental effects in X-ray fluorescence analysis. The measured X-ray fluorescence intensity has been expressed as a function of the different fluorescence elements composing the sample. this complex function has become an operative function via a Taylor series development. An explication has been given for the significance of the different terms of the series. These terms respond to mathematical functions known as characteristic functions for each chemical system. A parameter (B) has been defined which makes it possible to quantify the influence of the interelemental effect as a function of the analyte concentration (C) and that of the concomitant elements. The proposed model has been applied to the Fe-Zr-diluent chemical system. Simple relationships between B vs C have been obtained independently considering iron or zirconium as analyte.

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.

We present results of an experiment using decelerated U91+ ions, extracted from the GSI-ESR storage ring, and transmitted through a thin silicon crystal in channeling conditions. Charge state at emergence, secondary electron multiplicity and X-rays are measured simultaneously. These conditions allow to study the competition between mechanical electron capture (MEC) and radiative electron capture (REC) as a function of impact parameter. We observe that REC is the dominant charge exchange process for the best channeled ions, i.e. those travelling always far from the silicon target core electrons. For ions with high transverse energy, MEC into highly excited states is counterbalanced by enhanced ionization arising from a succession of close collisions along atomic rows.

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.

New journal of physics 20(7), 073033 (2018). doi:10.1088/1367-2630/aad01d, Published by IOP, [London]

This paper is a study of the interelemental effect and its correction based on the mathematical model used to develop LDM in XRF analysis. A “compensation coefficient” is defined which is obtained from the quotient of the mass absorption coefficients of the problem and the standard (μs*/μp*). This coefficient compensates the effects produced by interactions between the analyt and the interferences and therefore acts as a correction factor for the interelemental effect within this theoretical model. The model itself establishes a simple relation of the “compensation coefficient” and the Y/H correction parameters for the unknown and the standard. An algorithm is proposed for calculating the “compensation coefficient” following an algebraic procedure. The proposed method has been applied to XRF analysis of samples consisting of iron and zirconium mixtures and clays. In all cases a satisfactory correction of the interelemental effect has been achieved.

An algorithm for quantifying interelemental effects in X-ray fluorescence techniques is developed. By applying an addition process, the ratio between the mass absorption coefficients of the analyte and the unknown sample (μi*/μs*) is calculated to correct the fluorescence intensity of the element to be determined and linearize the I-c calibration plot. This coefficient can be calculated graphically and numerically. The method is applied to the determination of tin in lead alloys with good results over wide concentration ranges.

International audience; The experimental investigation of quantum-electrodydamic contributions to the binding energies of inner shells of highly charged heavy ions requires an accurate spectroscopy in the region of hard x-rays suitable at a limited source strength. For this purpose the focusing compensated asymmetric Laue crystal optics has been developed and a twin-spectrometer assembly has been built and commissioned at the experimental storage ring of the GSI Helmholtzzentrum Darmstadt. We characterize the crystal optics and demonstrate the usefulness of the instrumentation for accurate spectroscopy of both stationary and fast moving x-ray sources. The experimental procedures discussed here may also be applied for other spectroscopic studies where a transition from conventional germanium x-ray detectors to crystal spectrometers seems too demanding because of low source intensity.

The use of a sulfuric rather than a hydrochloric acid medium for the reduction of As(V) to As(III) by iodide is proposed. Optimum conditions of acid concentration, amount of sodium hydroxide, and time and temperature are established to achieve quantitative reduction. The optimized reduction procedure was applied to the iodimetric determination of total arsenic and compared to a procedure that employs a hydrochloric acid medium. A systematic error of 0.04% was found for the method with a sulfuric acid medium opposed to 0.05% for the method with a hydrochloric acid medium in the reduction step. The proposed modified iodimetric method has been successfully used with some organic samples requiring a prior destructive treatment of the organic matrix.

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.

Significant multiple electron capture has been found in collisions of 46 MeV/u Pb81+ ions with thin carbon foils. An increase in the many-electron capture probability has been observed for the thinnest targets, which is contrary to the normally assumed process of subsequent single-electron capture in the bulk. This shows the significant contribution of the surface for multiple electron capture. Further evidence is found for a strongly reduced capture probability from the exit surface as compared to the entrance surface. Absolute yields for electron capture and projectile ionization are presented and discussed within a Monte-Carlo simulation.

A novel method for direct, high precision mass measurements of relativistic exotic nuclei has been successfully applied in the storage ring ESR at GSI. The nuclei of interest were produced by projectile fragmentation of 930 MeV / u bismuth ions, separated in-flight by the fragment separator FRS, stored and cooled in the ESR. The mass values have been deduced from the revolution frequencies of the coasting cooled ions. We have measured 104 new mass values with a precision of about 100 keV and a resolving power of 3.5×10 5 for the neutron-deficient isotopes of the elements 57≤Z≤84 . This paper presents the experimental method, the mass evaluation and a table of the experimental mass values.

Two experimental methods of measuring masses of exotic nuclei in the storage ring ESR are presented. Bismuth and nickel fragments were produced via projectile fragmentation, separated and investigated with the combination of the fragment separator FRS and the ESR: (i) Direct mass measurements of relativistic projectile fragments were performed using Schottky mass spectrometry (SMS), i.e., exotic nuclei were stored and cooled in the ESR. Applying electron cooling, the relative velocity spread of circulating low intensity beams can be reduced below 10−6. Under this condition a mass resolving power of up to m/Δm=6.5·105 (FWHM) was achieved in a recent measurement. Previously unknown masses of more than 100 neutron-deficient isotopes have been measured in the range of 60≤Z≤84. Using known Q α values the area of known masses could be extended to more exotic nuclei and to higher proton numbers. The results are compared with mass models and extrapolations of experimental values. In a second experiment with 209Bi projectiles the area of the measured masses was extended to lower proton numbers. Due to various improvements at the ESR the precision of the measurements could be raised. (ii) Exotic nuclei with half-lives shorter than the time needed for SMS (present limit: T 1/2 ≈ 5 sec) can be investigated by time-of-flight measurements whereby the ESR is operated in the isochronous mode. This novel experimental technique has been successfully applied in first measurements with nickel and neon fragments where a mass resolving power of m/Δm=1.5·105 (FWHM) was achieved.

A method for the simultaneous spectrophotometric determination of calcium and magnesium in mineral waters with an FIA system is tested. The method is based on the reaction between the analytes and arsenazo(III) at pH 8.5. The calculations of the amounts of both analytes in the samples are carried out with the H-point standard addition method (HPSAM) for ternary mixtures, and with a partial least squares (PLS) model after a proper variable selection. The results obtained for the determination of calcium were comparable using both methods. The employment of the HPSAM brings to our attention the influence of the calcium concentration in the sample to the development of the reaction between magnesium and arsenazo(III). HPSAM also permits to estimate the concentration of magnesium in the samples.

A mathematical addition–dilution model for matrix correction was applied to the determination of iron(III), potassium and sulfur oxides in an industrial cement by XRF. The samples were prepared in the form of pellets. A cement of known composition was used as a single multi-element standard and the compactant and diluent was mannitol. The intensities were measured with an energy dispersive X-ray spectrometer. The graphical representation of intensityversus addition–dilution factor fits a hyperbolic function and, therefore, the proposed mathematical model can be applied. The results obtained by the proposed method show complete statistical agreement when compared with the content of the standard studied, which demonstrates that the method is suitable for this type of industrial sample with a complex matrix.

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.

Manganese can be determined by colorimetry with previous oxidation of Mn(II) in a strong basic medium, using 3,3′,5,5′-tetramethylbenzidine as a chromogenic reagent. The molar absorptivity of the reaction product is 3.4 × 104 mol−1l cm−1l, the detection limit 3 ng/ml, the RSD (0.5 mg/l,n = 8) 0.9% and the calibration range (1-cm cells) 0.02–0.8 mg/1 V(V), Cr(VI) and Co(II) are the most significant interferences. The new method was compared with an AAS procedure (air-acetylene flame) with previous solvent extraction and also with a colorimetric method for the determination of manganese in sea and drinking water.

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.

The ESR storage ring offers the unique opportunity to store and cool fully stripped heavy ions up to Uranium at energies between 50 and 370 MeV/u. Measurements of the longitudinal cooling force for several ion species from C 6+ to U 92+ are presented. A pronounced deviation from the expected q 2 scaling was found. Further investigations have been performed to study the influence of magnetic field strength on the longitudinal cooling force.

The use of 3,3',5,5'-tetramethylbenzidine (TMB) for residual chlorine determination in water offers 2 possibilities, one at pH 1-2 and absorbance measurement at 450 nm and another at pH 3.8-5.8 and measurement at 650 nm. The reaction of chlorine with TMB reaches its maximum sensitivity at pH 1-2. The detection limit is 2 ng/mL. A calibrated scale for colorimetric determination of residual chlorine in water with 3,3',5,5'-tetramethylbenzidine (TMB), prepared with tropaeolin O (C.I. 14270), is described. This scale is stable for several months and can be useful in replacing the conventional and much less stable scale prepared from standard solutions of oxochlorate (I). Kits for determination of residual chlorine in water by visual comparison, including a 3-dimensional scale or a color scale printed on paper or a plastic material, are described in this article. A comparative study of the analytical qualities and applications of the TMB methods against other reagents methods is performed.

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.

X-rays are emitted with the radiative recombination of free electrons in an electron cooler of a heavyion storage ring. Due to a small width of the X-ray lines, an observation angle close to 0° and an accurate determination of the ion velocity, the ground-state Lambshift of hydrogenlike uranium (470 ± 16) eV could be measured to an accuracy of 3.4%. A re-evaluation of a measurement of the 1s 1/2 Lambshift in hydrogenlike gold gave a new value of (202.3 ± 7.9) eV as compared to the former value of (212 ± 15) eV. The results are in excellent agreement with QED calculations and are more precise than any other measurements previously reported for a high-Z, hydrogenlike ion.

Dielectronic recombination (DR) of Be-like 136Xe50+ was measured by employing the electron-ion merged-beam technique at the storage ring ESR of GSI in Darmstadt, Germany. We present results covering the center-of-mass energy range 0 − 4 eV. In addition to Rydberg series of resonances associated with ground-state intra L-shell excitations, resonances were found which are formed during DR of initially metastable 136Xe50+(2s2p 3P0) parent ions. This state is the first excited state and is long lived because the J=0 → J=0 transition and the absence of nuclear spin make the rare E1M1 two-photon transition the lowest-order decay channel. Future measurements which will monitor the strength of the resonances as function of storage time may be exploited for a measurement of the E1M1 two photon transition rate.

A study of neutron-rich isotopes in the A=185 region of the nuclear chart has uncovered long-lived (>1 s) isomers in several isotopes of hafnium, tantalum, tungsten, rhenium, and osmium. The region was accessed via the use of projectile fragmentation with the UNILAC-SIS accelerators at GSI. Fragmentation products of 197Au were passed through the fragment separator (FRS) and injected into the experimental storage ring (ESR), where single-ion identifications could be made. Evidence is presented for isomers in 183,184,186Hf, 186,187Ta, 186W, 190,192,194Re, and 195Os with excitation energies in the range of 0.1–3.0 MeV. The lightest of these nuclides have well deformed prolate shapes, while the heaviest are transitional and susceptible to shape changes. Their properties are interpreted with the help of multi-quasiparticle and potential-energy-surface calculations.

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.

A method for correcting the intensity of x-ray fluorescence (limit dilution method) is proposed for the analysis of samples with a complex matrix such as ceramic materials of archaeological interest. This method corrects the interelement effects, resolving the wide deviations which occur in the quantitative results obtained by x-ray fluorescence without correction. The contents of sodium, magnesium, aluminium, silicon, potassium, calcium, titanium and iron in sixteen archaeological ceramic samples of different origins and from different locations were determined. The results obtained are comparable to the values obtained by chemical analysis. A statistical study of the data was carried out to classify the samples hierarchically by cluster analysis of their chemical composition and loss on ignition.

The heavy ion synchrotron/storage ring facility at GSI, SIS/ESR, provides intense beams of cooled, highly-charged ions up to naked uranium (U92+). By electron capture during ion-atom collisions in the gas target of the ESR or by recombination at ion-electron encounters in the "electron cooler" excited states are populated. The detailed structure of very heavy one-, two-and three-electron ions is studied. The different mechanisms leading to the excited states are described, as well as the new experimental tools now available for a detailed spectroscopy of these interesting systems. Special emphasis is given to x-ray transitions to the groundstates in H- and He-like systems. For the heaviest species the groundstate Lambshift can now be probed on an accuracy level of better than 10% using solid-state x-ray detectors. Applying dispersive x-ray analysing techniques, this accuracy will certainly be improved in future. However, utilizing the dielectronic recombination resonances for a spectroscopy, the structure in Li-like heavy ions can already be probed now on the sub eV level.

A new spectrophotometric method was developed to determine vanadium using tannic acid as a complexing reagent to form a coloured reaction product which can easily be extracted by 1-pentanol in the presence of cetylpyridinium. The developed method can successfully be applied to determine trace levels of 10 ng/ml of vanadium in natural waters without any preconcentration step. It can also determine less than 1 mg/kg of vanadium in edible oils and petroleum products.

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.