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The three dimensional 3D microstructural evolution of A206 AlCu4.5Mg0.3 and AlCu7 alloys is studied as function of solution treatment ST time by synchrotron tomography. 3D microstructural parameters of rigid phases such as volume fraction, interconnectivity volume of biggest aluminide total aluminide volume and contiguity touching surface are presented. In situ synchrotron tomography is carried during tensile deformation out to characterize the damage mechanisms and evolution

Recent spectroscopic models of active galactic nuclei have indicated that the recommended electron-ion recombination rate coefficients for iron ions with partially filled Mshells are incorrect in the temperature range where these ions form in photoionized plasmas. We have investigated this experimentally for Fe7+ forming Fe6+, Fe8+ forming Fe7+, and Fe13+ forming Fe12+. The recombination rate coefficient was measured employing the electron-ion merged beams method at the Heidelberg heavy-ion storage-ring TSR. The measured energy range encompassed at least all dielectronic recombination (DR) resonances associated with core excitations within the M-shell of the parent ions. Already in our first measurement, that is for Fe13+, we find unusually strong DR resonances at low electron-ion collision energies leading to low temperature plasma DR rate coefficients orders of magnitude larger than the recommended rate coefficient

We have measured resonance strengths and energies for dielectronic recombination (DR) of beryllium-like Fe XXIII forming boron-like Fe XXII via N = 2 → N' = 2 and N = 2 → N' = 3 core excitations. All measurements were carried out using the heavy-ion Test Storage Ring at the Max Planck Institute for Nuclear Physics (MPI-K) in Heidelberg, Germany. We have also calculated these resonance strengths and energies using three independent, perturbative, state-of-the-art theoretical techniques: the multiconfiguration Breit-Pauli (MCBP) method, the multiconfiguration Dirac-Fock (MCDF) method, and the Flexible Atomic Code (FAC). Overall reasonable agreement is found between our experimental results and these theoretical calculations. We have used our measurements to produce a Maxwellian-averaged DR rate coefficient for Fe XXIII. Our experimentally derived rate coefficient is estimated to be accurate to better that ≈20%. At temperatures where Fe XXIII is predicted to form in both photoionized and electron-ionized gas, we find mixed agreement between our experimental rate coefficient and previously published rate coefficients. We find good agreement at these temperatures between the experimentally derived rate coefficient and our MCBP, MCDF, and FAC results.

Using the Oak Ridge National Laboratory ion-atom merged-beams apparatus, the absolute total electron-capture cross section has been measured for collisions of Ne4+ with hydrogen and deuterium at relative energies in the center-of-mass frame between 0.10 and 1006 eV/u. Comparison with previous measurements shows large discrepancies between 80 and 600 eV/u. For energies below ∼1 eV∕u, a sharply increasing cross section is attributed to the ion-induced dipole attraction between the reactants. Multichannel Landau-Zener calculations are performed between 0.01 and 5000 eV/u and compare well to the measured total cross sections. Below ∼5 eV∕u, the present total cross section calculations show a significant target isotope effect. At 0.01 eV/u, the H:D total cross section ratio is predicted to be ∼1.4 where capture is dominated by transitions into the Ne3+ (2s22p23d) configuration.

Am Testspeicherring TSR wurden Rekombinationsexperimente an berylliumähnlichen Ionen mit energiescharfen, freien Elektronen mittels der merged-beam Technik durchgeführt. Neben der dominanten dielektronischen Rekombination (DR) wurde erstmalig der Prozess der trielektronischen Rekombination (TR) für Delta N = 0 Übergänge nachgewiesen, bei welcher der strahlungslose Elektroneneinfang unter gleichzeitiger Anregung zweier Targetelektronen erfolgt. Die Stärke des TR-Wirkungsquerschnitts hängt stark ab von der Abwesenheit erlaubter Verlustkanäle, über welche der dreifach angeregte TR-Zwischenzustand in die Kontinua einfach angeregter Targetelektronenkonfigurationen zerfallen kann. Entlang einer TR-Rydbergserie fallen die Resonanzstärken beim Überschreiten der DR-Seriengrenzen um jeweils mehrere Grössenordnungen ab. Die experimentellen Spektren zeigen einen bevorzugten Zerfall der Rumpfelektronen innerhalb gleicher Spinmultiplizitäten. Oberhalb der Triplett DR-Seriengrenzen werden daher innerhalb der experimentellen Empfindlichkeit keine Triplett TR-Resonanzen und jenseits der Singulett DR-Seriengrenze auch keine Singulett TR-Resonanzen mehr beobachtet. Mit AUTOSTRUCTURE erstellte Modellspektren ermöglichen im Vergleich mit den experimentellen Daten ein tieferes Verständnis für den TR-Prozess. Es konnte gezeigt werden dass mit zunehmender Kernladungszahl das Interkombinationsverbot für die Autoionisation aufgrund der intermediären Kopplung nicht mehr strikt gilt. Bei den schweren Ionen lassen sich aufgrund der zunehmenden Aufspaltung der einfach angeregten Triplettzustände zu den Dipolübergängen analoge Auswahlregeln erkennen. Insgesamt wird der TR-Wirkungsquerschnitt jedoch für höhere Drehimpulsquantenzahlen des Valenzelektrons von der Theorie prinzipiell unterschätzt.

The basic approach for measuring electron-ion recombination rate coefficients in merged-beams electron-ion collision experiments at heavy-ion storage rings is outlined. As an example experimental results for the low temperature recombination of C IV ions are compared with the recommended theoretical rate coefficient by Mazzotta et al. The latter deviates by factors of up to 5 from the experimental one., Comment: 5 pages, 3 figures, Workshop on Stellar Coronae in the Chandra and XMM-Newton era, June 2001, Noordwijk, The Netherlands, for a recent theoretical treatment of C IV DR see Pradhan and al., Phys. Rev. Lett. 87, 183201 (2001)