Radiative Electron Capture into High- Z Few-Electron Ions: Alignment of the Excited Ionic States

We lay out a unified formalism for the description of radiative electron capture into excited states of heavy, few-electron ions and their subsequent decay, including a full account of many-electron effects and higher-order multipoles of the radiation field. In particular, the density-matrix theory is applied to explore the magnetic sublevel population of the residual ions, as described in terms of alignment parameters. For the electron capture into the initially hydrogenlike U91+ and lithiumlike U89+ uranium projectiles, the alignment parameters are calculated, within the multiconfiguration Dirac-Fock approach, as a function of the collision energy and for different ionic states. From these calculations, we find that the many-electron interactions may result in a small enhancement of the alignment, and that this effect becomes more pronounced for highly excited levels

Angular and Polarization Analysis of X-Rays Emitted from Highly-Charged, Few-Electron Ions

The recent theoretical progress in studying the x-ray emission from highly-charged, few-electron ions is reviewed. These case studies show that relativistic, high-Z ions provide a unique tool for better understanding the interplay between the electron-photon and electron-electron interactions in strong fields. Most naturally, this interplay is probed by the radiative capture of a (quasi-) free electron into the bound states of projectile ions, and by varying the charge state and the energy of the projectiles. For the capture into initially hydrogen-and lithium-like ions, here we summarize the recent results for the angular distribution and polarization of the recombination photons as well as the subsequent Kα emission, if the electron is captured into an excited state of the ion

K α₁ Radiation from Heavy, Heliumlike Ions Produced in Relativistic Collisions

Bound-state transitions in few-electron, heavy ions following radiative electron capture are studied within the framework of the density matrix theory and the multiconfiguration Dirac-Fock approach. Special attention is paid to the K α1 (1 s1/2 2 p3/2 1.3PJ=1,2→1s21/2 1SJ=0) radiative decay of heliumlike uranium U90+ projectiles. This decay has recently been observed at the GSI facility in Darmstadt, giving rise to a surprisingly isotropic angular distribution, which is inconsistent with previous experiments and calculations based on a one-particle model. We show that the unexpected isotropy essentially results from the mutual cancellation of the angular distributions of the 1P1 → 1S0 electric dipole and 3P2 → 1S0 magnetic quadrupole transitions, both of which contribute to the K α1 radiation. Detailed computations on the anisotropy of the K α1 radiation have been carried out for a wide range of projectile energies and are compared to available experimental data

Effects of Configuration Interaction on the Alignment of Beryllium-Like Ions

The radiative electron capture into (initially) lithium-like ions is studied within the framework of the density matrix approach. Special attention is paid to the magnetic sublevel population of the residual ionic states which is described by a set of alignment parameters. Detailed calculations of these parameters have been performed for the capture into the 1s2 2s 3d3/2 Jf2 level of high-Z ions along the beryllium isoelectronic sequence. We devote special attention to the modifications in the many-electron case as opposed to singleelectron systems. The electron correlation leads to an enhancement of the alignment, which becomes more pronounced as the nuclear charge decreases and the electron-electron interaction gains in strength as compared to the electron-nucleus interaction

Reprocessing of Instruments for Minimal Invasive Surgery - State of the Art and Prospects

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Die Weiterentwicklung des Instrumentariums der minimal-invasiven Chirurgie (MIC) vollzieht sich in Richtung einer Miniaturisierung mechanischer Komponenten, einer Kombination mehrerer Funktionen in einem Gerät und der Einführung neuer Techniken, insbesondere zur blutungsarmen und thermisch schonenden Durchtrennung von Blutgefäßen. Diese Entwicklungstendenzen haben Auswirkungen auf die Aufbereitungsfähigkeit der Geräte. Sie wirken sich in der Regel erschwerend aus. Hierbei stellt insbesondere die Reinigung, also die Entfernung der Anschmutzungen aus kleinen Lumina, filigranen Gelenken, von der Waschflotte schwer erreichbaren Toträumen etc. besonders hohe Anforderungen. Hinzu kommt, daß der Nachweis des Reinigungserfolges schwer zu führen ist und bisher kein in der Routine praktikables, allgemein akzeptiertes Standardnachweisverfahren eingeführt werden konnte. Es werden ein Überblick über die im Zusammenhang mit der Aufbereitung von Instrumenten der MIC auftretenden Problemstellungen gegeben und Lösungsansätze diskutiert.The development of instruments for minimal invasive surgery (MIS) is moving in the direction of the miniaturization of mechanical components, a combination of multiple functions in a single instrument, and the introduction of new techniques, in particular those reducing bleeding and thermal damage when cutting blood vessels. These tendencies have consequences for the reprocessability of the instruments, usually making reprocessing more difficult. In particular cleaning the removal of contaminations from tiny lumina, joints, etc., is highly demanding. In addition, proof of successful cleaning is difficult, and no standardised method of doing this in practice is currently available. An overview of the problems associated with the reprocessing of instruments for minimal invasive surgery is given, and a numbers of possible solutions are discussed

On the Nature of Soft X-ray Weak Quasi-Stellar Objects

Recent studies of QSOs with ROSAT suggest the existence of a significant population of Soft X-ray Weak QSOs (SXW QSOs) where the soft X-ray flux is ~ 10-30 times smaller than in typical QSOs. As a first step in a systematic study of these objects, we establish a well-defined sample of SXW QSOs which includes all alpha_ox<=-2 QSOs from the Boroson & Green (1992) sample of 87 BQS QSOs. SXW QSOs comprise about 11% of this optically selected QSO sample. From an analysis of CIV absorption in the 55 BG92 QSOs with available CIV data, we find a remarkably strong correlation between alpha_ox and the CIV absorption equivalent width. This correlation suggests that absorption is the primary cause of soft X-ray weakness in QSOs, and it reveals a continuum of absorption properties connecting unabsorbed QSOs, X-ray warm absorber QSOs, SXW QSOs and BAL QSOs. From a practical point of view, our correlation demonstrates that selection by soft X-ray weakness is an effective (>=80% successful) and observationally inexpensive way to find low-redshift QSOs with strong and interesting ultraviolet absorption. We have also identified several notable differences between the optical emission-line properties of SXW QSOs and those of the other BG92 QSOs. SXW QSOs show systematically low [O III] luminosities as well as distinctive H-beta profiles. They tend to lie toward the weak-[O III] end of BG92 eigenvector 1, as do many low-ionization BAL QSOs. Unabsorbed Seyferts and QSOs with similar values of eigenvector 1 have been suggested to have extreme values of a primary physical parameter, perhaps mass accretion rate relative to the Eddington rate (M-dot/M-dot_{Edd}). If these suggestions are correct, it is likely that SXW QSOs also tend to have generally high values of (M-dot/M-dot_{Edd}). (Abridged)Comment: 34 pages, ApJ accepted, also available from http://www.astro.psu.edu/users/niel/papers/papers.htm

Alignment of Heavy Few-Electron Ions Following Excitation by Relativistic Coulomb Collisions

The Coulomb excitation of highly charged few-electron ions in relativistic collisions with protons and low- Z atoms is studied within the framework of first-order perturbation theory and the multiconfiguration Dirac-Fock method. Apart from the computation of the total excitation cross sections, a detailed theoretical analysis has been performed for the magnetic sublevel population of the residual ions. To describe this population, general expressions are derived for the alignment parameters of the excited states of the ions, taking into account the relativistic and many-electron effects. Calculations are performed for the K→L and K→M excitation of helium- and lithiumlike uranium ions and for a wide range of projectile energies. It is shown that the alignment of heavy few-electron ions is sensitive to relativistic and magnetic-interaction effects and, hence, to the collision energies of the projectiles. The theoretical predictions are discussed in the context of recent measurements on the Coulomb excitation of heliumlike uranium U90+ ions which were recently performed at the GSI storage ring in Darmstadt

Multipole Expansion of Bremsstrahlung in Intermediate Energy Heavy Ion Collisions

Using a multipole expansion of the radiated field generated by a classical electric current, we present a way to interprete the bremsstrahlung spectra of low energy heavy ion collisions. We perform the calculation explicitely for the system ^{12}C+ ^{12}C at 84AMeV and compare the result with the experimental data of E. Grosse et al. Using simple model assumptions for the electromagnetic source current we are able to describe the measured data in terms of coherent photon emission. In this context, the information contained in the measured data is discussed.Comment: LaTex, 4 Figure

Application of technetium and rhenium carbonyl chemistry to nuclear medicine. Preparation of [NEt4]2[TcCl3(CO)3] from [NBu4][TcO4] and structure of [NEt4][Tc2(μ-Cl)3(CO)6]; structures of the model complexes [NEt4][Re2(μ-OEt)2(μ-OAc)(CO)6] and [ReBr({-CH2S(CH2)2Cl}2)(CO)3]

A detailed investigation of the one-pot synthesis of [NEt4]2[MX3(CO)3] [M=Tc (1a) or Re (1b); X= Cl−, Br−] is presented. The intermediates [NEt4][Tc2-(μ-Cl)3(CO)6] (2a), [NBu4][Tc3(μ3-H)(μ-H)3(CO)9] (3) and [Tc3(μ-H)3(CO)12] (4) have been isolated and characterized. The X-ray structure of (2a) is described. Complex (2a) crystallizes in the monoclinic space group P21/c with a=19.491(6), b=18.323(2) and c=17.497(9)AÅ, and β=97.59(2)°. Quantitative conversion of (2a), (3) and (4) into the aqua-ion [M(OH2)3(CO)3]+ [M=Tc (5a) or Re (5b)] is described. To evaluate an optimal and simple chelating group for the "fac-M(CO)3” moiety, the reaction with the bidentate thioether ligand Cl(CH2)2S(CH2)2S(CH2)2Cl (qyp) has been investigated and the structure of the neutral complex [ReBr(qyp)(CO)3] (6) is described. Complex (6) crystallizes in the monoclinic space group P21/c with a=15.935(6), b=2.788(4) and c= 7.955(10)AÅ, and β=98.57(1)°. To extend the knowledge about substitution chemistry of organometallic complexes in aqueous solution, the acetato ligand [OOCCH3]− has been reacted with (1b), resulting in the formation of the dinuclear, acetato-bridged complex [NEt4][Re2(μ-OH)2(μ-OAc)(CO)6], which converted into [Re2(μ-OEt)2(μ-OAc)(CO)6]− (7) after recrystallization from EtOH. The X-ray structure of (7) has been determined. Complex (7) crystallizes in the monoclinic space group P21/c with a=16.288(3), b=12.4272(10) and c=13.620(3)AÅ, and β=76.63(1)°. For a future application of the small "fac-M(CO)3” moiety, it seems thus advantageous to combine these two ligand groups in one simple chelating functio