Branching ratios of x-ray photons from dielectronic recombination processes in H-like titanium ions

In dielectronic recombination of hydrogenlike ions an intermediate doubly excited heliumlike ion is formed. Since the K shell is empty, both excited electrons can decay sequentially to the ground state. In this paper we analyze the x-ray radiation emitted from doubly and singly excited heliumlike titanium ions produced inside the Tokyo electron beam ion trap. Theoretical population densities of the singly excited states after the first transition and the transition probabilities of these states into the ground state were also calculated. This allowed theoretical branching ratios to be determined for each manifold. These branching ratios are compared to the experimentally obtained x-ray distribution by fitting across the relevant peak using a convolution of the theoretically obtained resonance strengths and energies. By taking into account 2E1 transitions which are not observed in the experiment, the measured and calculated ratios agree well. This method provides a valuable insight into the transition dynamics of excited highly charged ions.

Effective collision strengths for transitions of Ni XVII

Electron impact excitation collision strengths are required for the analysis and interpretation of stellar observations. This calculation aims to provide fine structure effective collision strengths for the Ni XVII ion using a method which includes contributions from resonances. A DARC calculation has been performed, involving 37 J pi states. The effective collision strengths are calculated by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. The non-zero effective collision strengths for transitions between the fine structure levels are given for electron temperatures (T(e)) in the range log(10) T(e)(K) = 4.5 - 8.5. Data for several transitions from the ground state are discussed in this paper.

MEASUREMENT AND CALCULATION OF ABSOLUTE SINGLE AND MULTIPLE CHARGE EXCHANGE CROSS SECTIONS FOR Feq+ IONS IMPACTING H2O

Charge exchange (CE) plays a fundamental role in the collisions of solar- and stellar-wind ions with lunar and planetary exospheres, comets, and circumstellar clouds. Reported herein are absolute cross sections for single, double, triple, and quadruple CE of Feq+ (q = 5-13) ions with H2O at a collision energy of 7q keV. One measured value of the pentuple CE is also given for Fe9+ ions. An electron cyclotron resonance ion source is used to provide currents of the highly charged Fe ions. Absolute data are derived from knowledge of the target gas pressure, target path length, and incident and charge-exchanged ion currents. Experimental cross sections are compared with new results of the n-electron classical trajectory Monte Carlo approximation. The radiative and non-radiative cascades following electron transfers are approximated using scaled hydrogenic transition probabilities and scaled Auger rates. Also given are estimates of cross sections for single capture, and multiple capture followed by autoionization, as derived from the extended overbarrier model. These estimates are based on new theoretical calculations of the vertical ionization potentials of H2O up to H2O10+.

ABSOLUTE DOUBLY DIFFERENTIAL CROSS-SECTIONS FOR ELECTRON-EMISSION IN COLLISIONS OF 3.5-MEV/U FE(17+) AND FE(22+) IONS WITH HE AND AR GAS TARGETS

Absolute doubly differential cross sections have been measured as a function of electron energy and angle of observation for electron emission in collisions of 3.5-MeV/u Fe17+ and Fe22+ ions with He and Ar gas targets under single-collision conditions. The measured electron emission cross sections are compared to theoretical and scaled cross sections based on the Born approximation. The results using intermediate-mass ions are discussed with reference to previously reported cross sections from collisions with highly charged lighter- and heavier-ion species at MeV/u projectile energies. The continuum-distorted-wave-eikonal-initial-state approximation shows good agreement with experiments except in the

CROSS-SECTIONS FOR RESONANT TRANSFER AND EXCITATION IN FEQ++H-2 COLLISIONS

Resonant transfer and excitation (RTE) is investigated for Fe(q+) ions (q=23, 24, and 25) colliding with H2. For each charge state, cross sections for RTE were obtained from measurements of K x rays, emitted from the doubly excited intermediate state, coincident with single-electron capture by the incident ion. Additionally, for Fe25+ cross sections were obtained from measurements of coincidences between the two K x rays emitted from the intermediate state. These latter measurements Provide information on the lifetimes of intermediate metastable states formed in the RTE process. In all cases, measured cross sections are in good agreement with calculations based on theoretical cross sections for dielectronic recombination (DR). Since RTE closely approximates DR, the results indicate that dielectronic-recombination cross sections involving K-shell excitation can be accurately predicted for highly charged iron ions. The results for Fe25+ show that metastable states are sufficiently short lived to be observable in the RTE (or DR) process for these hydrogenlike ions.

Precision laser spectroscopy of the ground state hyperfine splitting of hydrogenlike ^209 Bi^82+

The first direct observation of a hyperfine splitting in the optical regime is reported. The wavelength of the M1 transition between the F = 4 and F = 5 hyperfine levels of the ground state of hydrogenlike ^209 Bi^82+ was measured to be \lamda_0 = 243.87(4) nm by detection of laser induced fluorescence at the heavy-ion storage ring ESR at GSI. In addition, the lifetime of the laser excited F = 5 sublevel was determined to be \tau_0 = 0.351(16) ms. The method can be applied to a number of other nuclei and should allow a novel test of QED corrections in the previously unexplored combination of strong magnetic and electric fields in highly charged ions.

Avaliação do potencial antiinflamatório, anticoagulante e hemorrágico de heparinóides presentes em "Artemia franciscana"

Heparan sulfate (HS) and Heparin (Hep) glycosaminoglycans (GAGs) are heterogeneous and highly charged polysaccharides. HS is structurally related to Hep but is much less substituted with sulfo groups than heparin and has a more varied structure (or sequence). Because of structural similiarities between these two polymers, they have been described together as heparinoids . Both chains bind a variety of proteins and mediate various physiologically important processes including, blood coagulation, cell adhesion and growth factor regulation. Heparinoids with structural characteristics similar to these described from HS and/or Hep from mammalian tissues have been isolated from different species of invertebrates, although only a few heparinoids from unusual sources have been characterized. The present study describes the presence of unusual heparinoids population from Artemia franciscana, isolated after proteolysis and fractionation by ion exchange resin and named, F-3.0M. The study model in vivo were hemostasis (rat tail scarification) and inflamatoty activity. The tests in vitro were used for coagulations assays (PT and APTT). The analyse of the heparinoids eluted with 3,0M NaCl showed electrophoretic migration in different buffer systems a single band with a behaviour intermediate between those of mammalian HEP and HS. The main products obtained from Artemia heparinoids after enzymatic degradation with heparitinases I and II from F. heparinum were N-sulphated disaccharides (∆U-GlcNS,6S/ ∆U,2S-GlcNS and ∆U-GlcNS) and N-acetylated disaccharides (∆U, GlcNAc). This heparinoid had a lower hemorrhagic effect (400μg/ml) when compared to unfractiionated heparins(25μg/ml).The results also suggest a negligible APTT activity of this heparinoid (62.2s). No action was observed on PT indicating that F-3.0M haven t action on the extrinsic pathway. The results showed that the fraction F- 3.0M have inhibitory effect on migration of leukocytes, 64.5% in the concentration of 10 μg/ml (P<0.001). The search for new heparin and/or heparan sulphates analogs devoid of anticoagulant activity is an atractive alternative and may open up a wide variety of new therapeutic applications

A critical investigation of the Tanford-Kirkwood scheme by means of Monte Carlo simulations

Monte Carlo simulations are used to assess the adequacy of the Tanford-Kirkwood prescription for electrostatic interactions in macromolecules. Within a continuum dielectric framework, the approach accurately describes salt screening of electrostatic interactions for moderately charged systems consistent with common proteins at physiological conditions. The limitations of the Debye-Huckel theory, which forms the statistical mechanical basis for the Tanford-Kirkwood result, become apparent for highly charged systems. It is shown, both by an analysis of the Debye-Huckel theory and by numerical simulations, that the difference in dielectric permittivity between macromolecule and surrounding solvent does not play a significant role for salt effects if the macromolecule is highly charged. By comparison to experimental data, the continuum dielectric model (combined with either an approximate effective Hamiltonian as in the Tanford-Kirkwood treatment or with exact Monte Carlo simulations) satisfactorily predicts the effects of charge mutation on metal ion binding constants, but only if the macromolecule and solvent are assigned the same or similar permittivities.

Präzisionsmessung des magnetischen Moments des Elektrons in wasserstoffähnlichem Kohlenstoff

In dieser Arbeit wird eine Messung des magnetischen Moments des Elektronsin wasserstoffähnlichem Kohlenstoff vorgestellt. Das Ergebnis derMessungen an einem einzelnen gespeicherten¹²C⁵⁺-Ionist: g = 2,001 041 596 4 (8)(6)(44). Der erste Fehler bezeichnet die statistischeUnsicherheit, der zweite Fehler die systematische Unsicherheit. Der letzteFehler resultiert aus der Unsicherheit des Verhältnisses der Massedes ¹²C⁵⁺-Ions und der des Elektrons. Die hohe Genauigkeitder Messung wurde durch die räumliche Trennung des Nachweises derAusrichtung des Spins und des Induzierens der spin-flips erreicht. DieMessung stellt die bisher genaueste Bestimmung eines atomaren g-Faktorsdar und bestätigt den theoretischen Wert der Göteborger Theoriegruppeauf 7*10^-9. Zusammen mit diesen Rechnungen verifiziert sie dieBound-State-QED-Korrekturen genauer als 1%. Somit ist der g-Faktor desin¹²C⁵⁺ gebunden Elektrons neben Messungen der Lambshiftin schweren hochgeladenen Ionen der genaueste Test der Bound-State-QED.
Wird auf die Richtigkeit der Berechnung des g-Faktors des gebundenenElektrons vertraut, kann folgender Wert für die atomare Masse desElektrons gewonnen werden: m_e= 0,000 548 579 912 8 (15) u.

Mode coupling for precise measurements of the electronic g-factor of hydrogen-like ions in Penning traps

The g-factor is a constant which connects the magnetic moment $vec{mu}$ of a charged particle, of charge q and mass m, with its angular momentum $vec{J}$. Thus, the magnetic moment can be writen $ vec{mu}_J=g_Jfrac{q}{2m}vec{J}$. The g-factor for a free particle of spin s=1/2 should take the value g=2. But due to quantum electro-dynamical effects it deviates from this value by a small amount, the so called g-factor anomaly $a_e$, which is of the order of $10^{-3}$ for the free electron. This deviation is even bigger if the electron is exposed to high electric fields. Therefore highly charged ions, where electric field strength gets values on the order of $10^{13}-10^{16}$V/cm at the position of the bound electron, are an interesting field of investigations to test QED-calculations. In previous experiments [H"aff00,Ver04] using a single hydrogen-like ion confined in a Penning trap an accuracy of few parts in $10^{-9}$ was obtained. In the present work a new method for precise measurement of magnetic the electronic g-factor of hydrogen-like ions is discussed. Due to the unavoidable magnetic field inhomogeneity in a Penning trap, a very important contribution to the systematic uncertainty in the previous measurements arose from the elevated energy of the ion required for the measurement of its motional frequencies. Then it was necessary to extrapolate the result to vanishing energies. In the new method the energy in the cyclotron degree of freedom is reduced to the minimum attainable energy. This method consist in measuring the reduced cyclotron frequency $nu_{+}$ indirectly by coupling the axial to the reduced cyclotron motion by irradiation of the radio frequency $nu_{coup}=nu_{+}-nu_{ax}+delta$ where $delta$ is, in principle, an unknown detuning that can be obtained from the knowledge of the coupling process. Then the only unknown parameter is the desired value of $nu_+$. As a test, a measurement with, for simplicity, artificially increased axial energy was performed yielding the result $g_{exp}=2.000~047~020~8(24)(44)$. This is in perfect agreement with both the theoretical result $g_{theo}=2.000~047~020~2(6)$ and the previous experimental result $g_{exp1}=2.000~047~025~4(15)(44).$ In the experimental results the second error-bar is due to the uncertainty in the accepted value for the electron's mass. Thus, with the new method a higher accuracy in the g-factor could lead by comparison to the theoretical value to an improved value of the electron's mass. [H"af00] H. H"affner et al., Phys. Rev. Lett. 85 (2000) 5308 [Ver04] J. Verd'u et al., Phys. Rev. Lett. 92 (2004) 093002-1

First Ramsey-type mass measurements with ISOLTRAP and design studies of the new PENTATRAP project

Der Einsatz von Penningfallen in der Massenspektrometrie hat zu einem einmaligen Genauigkeitssprung geführt. Dadurch wurden Massenwerte verschiedenster Atome zu wichtigen Eingangsparametern bei immer mehr physikalischen Fragestellungen. Die Massenspektrometrie mit Hilfe von Penningfallen basiert auf der Bestimmung der freien Zyklotronfrequenz eines Ions in einem homogenen Magnetfeld νc=qB/(2πm). Sie wird mit Flugzeitmethode (TOF-ICR) bestimmt, wobei eine relative Massenungenauigkeit δm/m von wenigen 10^-9 bei Nukliden mit Lebensdauern von <500 ms erreicht wird. Dies wurde durch die im Rahmen dieser Arbeit erstmals in der Penningfallen-Massenspektrometrie eingesetzten Ramsey-Methode möglich. Dabei werden zeitlich separierte, oszillierenden Feldern zur resonanten Ionenanregung genutzt, um die Frequenzmessung durch die Flugzeitmethode zu verbessern. Damit wurden am Penningfallenmassenspektrometer ISOLTRAP an ISOLDE/CERN die Massen der Nuklide 26,27Al und 38,39Ca bestimmt. Alle Massen wurden in die „Atomic Mass Evaluation“ eingebettet. Die Massenwerte von 26Al und 38Ca dienten insbesondere zu Tests des Standardmodells. Um mit Massenwerten fundamentale Symmetrien oder die Quantenelektrodynamik (QED) in extremen Feldern zu testen wurde ein neues Penningfallenprojekt (PENTATRAP) für hochpräzise Massenmessungen an hochgeladenen Ionen konzipiert. In dieser Doktorarbeit wurde vornehmlich die Entwicklung der Penningfallen betrieben. Eine Neuerung bei Penningfallenexperimenten ist dabei die permanente Beobachtung des Magnetfeldes B und seiner zeitlichen Fluktuationen durch so genannte „Monitorfallen“.

Ein Experiment zur Bestimmung des g-Faktors des gebundenen Elektrons in wasserstoff- und lithiumähnlichen mittelschweren Ionen

In dieser Arbeit werden der experimentelle Aufbau und erste Messungen für die Bestimmung des g-Faktors des Elektrons gebunden in wasserstoff- und lithiumähnlichen mittelschweren Ionen beschrieben. Mit dem hochpräzisenWert des g-Faktors können theoretische Berechnungen der Quantenelektrodynamik gebundener Zustände überprüft werden. Die Messungen werden in einem Dreifach-Penningfallen-System durchgeführt. Dort wurden im Rahmen dieser Arbeit auch erstmals hochgeladene Ionen bis 28Si13+ in einer hierfür entwickelten Elektronenstrahl-Ionenquelle/-falle erzeugt. Für die Bestimmung des g-Faktors werden die freie Zyklotronfrequenz und die Larmorfrequenz benötigt. Erstere wird aus den drei Eigenfrequenzen des in der Präzisionsfalle gespeicherten Ions berechnet. Um das Ion bei den Messungen nicht zu verlieren, werden die Eigenfrequenzen des Ions durch Kopplung an einen radiofrequenten Nachweisschwingkreis nicht-destruktiv nachgewiesen. Die freie Zyklotronfrequenz konnte dabei mit einer relativen Genauigkeit von wenigen 10E−9 bestimmt werden. Zur Bestimmung der Larmorfrequenz ist die genaue Kenntnis der Spinrichtung des Elektrons im Magnetfeld notwendig. Diese wird durch den kontinuierlichen Stern-Gerlach-Effekt in der sogenannten Analysefalle bestimmt. Hierzu muss eine hohe Stabilität der axialen Frequenz des Ions erreicht werden. Um dies sowie die Hochpräzisionsmessungen in der Präzisionsfalle zu erreichen, wurden in dieser Arbeit beide Fallen hinsichtlich ihrer elektrischen und magnetischen Eigenschaften charakterisiert.

Setup of a Penning trap for precision laser spectroscopy at HITRAP

Ion traps have been established as a powerful tool for ion cooling and laser spectroscopy experiments since a long time ago. SpecTrap, one of the precision experiments associated to the HITRAP facility at GSI, is implementing a Penning trap for studies of large bunches of externally produced highly charged ions. The extremely strong electric and magnetic fields that exist around the nuclei of heavy elements drastically change their electronic properties, such as energy level spacings and radiative lifetimes. The electrons can therefore serve as sensitive probes for nuclear properties such as size, magnetic moment and spatial distribution of charge and magnetization. The energies of forbidden fine and hyperfine structure transitions in such ions strongly depend on the nuclear charge and shift from the microwave domain into the optical domain. Thus, they become accessible for laser spectroscopy and its potentially high accuracy. A number of such measurements has been performed in storage rings and electron beam ion traps and yielded results with relative accuracies in the 10

Space Debris Removal with an Ion Beam Shepherd Satellite: target-plasma interaction

A novel concept for active space debris removal known as Ion Beam Shepherd (IBS) which has been recently presented by our group is investigated. The concept makes use of a highly collimated ion beam to exert the necessary force on a generic debris to modify its orbit and/or attitude from a safe distance in a controlled manner, without the need of docking. After describing the main characteristics of the IBS system, some of the key aspects of thruster plasma and its interaction with the debris are studied, namely, (1) the modeling of the expansion of an plasma beam, based on the quasi-selfsimilarity exhibited by hypersonic plumes, (2) the characterization of the force and torque exerted upon the target debris, and (3) a preliminary evaluation of other plasma-body interactions.