Showing papers by "Stephan Fritzsche published in 1999"
TL;DR: In this paper, a series of large-scale computations for these magnetic dipole and electric quadrupole transition probabilities were performed and compared with previous calculations and observed data on the separation of energy levels and transition probabilities for the four ions P I, S II, Cl III and Ar IV.
Abstract: Systematically enlarged multiconfiguration Dirac-Fock wave functions have been applied in order to investigate the forbidden lines among the 3s23p3 ground-state levels for phosphorus-like ions at the neutral end of the sequence. The probabilities and ratios of these lines are important in the diagnostics of astrophysical plasmas. In a recent computation by Keenan et al., these probabilities were found to differ by up to ~25% from earlier (partially semiempirical) computations. To analyze this discrepancy in the context of ab initio structure theory, we report on a series of large-scale computations for these magnetic dipole and electric quadrupole transition probabilities. Our computations do not confirm the deviations found by Keenan et al. Detailed comparisons are made with previous calculations and observed data on the separation of energy levels and transition probabilities for the four ions P I, S II, Cl III, and Ar IV. Our study clearly demonstrates the possibility of a systematic approach, but also shows the effort that is needed to obtain sufficiently accurate atomic data for systems with five (or more) valence electrons.
26 citations
TL;DR: Parpia et al. as discussed by the authors introduced a new package RATIP which extends GRASP92 towards the computation of various Relativistic Atomic Transition and Ionization Properties.
Abstract: Recent years have seen a growing number of large-scale atomic structure calculations using both nonrelativistic and relativistic theories. For investigations of multiple and highly charged ions, of course, a relativistic structure code like the widely known GRASP program is required. In a revised version of this program, namely GRASP92 (F A Parpia, C F Fischer and I P Grant 1996 Comput. Phys. Commun. 94 249), systematic studies of level energies and a few other bound-state properties are now being supported. — Here, we briefly introduce a new package RATIP which extends GRASP92 towards the computation of various Relativistic Atomic Transition and Ionization Properties. A short overview of the capabilities of RATIP along with current developments will be given.
7 citations
TL;DR: In this article, the authors performed beam-foil experiments on ions of the iron group at the Bochum Dynamitron tandem accelerator to identify the decays of long-lived levels with the help of Cowan Code and MCDF calculations.
Abstract: Beam-foil experiments on ions of the iron group have been done at the Bochum Dynamitron tandem accelerator. For elements Mn to Ge, prompt and delayed EUV spectra have been recorded in order to disentangle the contributions from short-lived and long-lived levels, in Cl-, S-, P- and Si-like ions. A number of decays of long-lived levels have been identified with the help of Cowan Code and MCDF calculations.
5 citations
TL;DR: In this article, the authors discuss the Ubergangswahrscheinlichkeiten der Interkombinationsubergange (i.e., InterkOMB) zwischen Systemen with verschiedenem Gesamtspin, or with gleicher Paritat als spektroskopisch „verboten” or doch zumindest als exotisch.
Abstract: Als Helium zu Beginn des Jahrhunderts im Labor spektroskopisch untersucht wurde, schien es zwei vollig getrennte Termsysteme aufzuweisen, ein Singulett-System, in dem die Spins der beiden Elektronen antiparallel stehen (Gesamtspin S = 0) und ein Triplett-System mit parallel ausgerichteten Elektronenspins (S = 1). Diese beiden Termsysteme lassen sich mit Hilfe des Elektronenspins einfach erklaren. Lange Zeit galten aber Ubergange zwischen Systemen mit verschiedenem Gesamtspin — sogenannte Interkombinationsubergange — oder mit gleicher Paritat als spektroskopisch „verboten” oder doch zumindest als exotisch. Heute werden gerade diese Ubergange fur die Diagnose von Plasmen auf der Erde und im Weltall genutzt. Nachdem fur diese schwachen Linien viele Jahre lang nur grobe Abschatzungen der Ubergangswahrscheinlichkeiten moglich waren, gelangen kurzlich prazise Messungen am Schwerionen-Speicherring und an einer Elektronenstrahl-Ionenfalle. Diese fordern die Theorie nun zu sehr aufwendigen Strukturrechnungen heraus.
TL;DR: In this article, the simultaneous excitation-ionization and excitation capture processes in collisions of 223 MeV/u He-like uranium ions with heavy target atoms are identified by measuring the x-ray (L? K) transitions in coincidence with projectiles undergoing charge exchange.
Abstract: The simultaneous excitation-ionization and excitation-capture processes in collisions of 223 MeV/u He-like uranium ions with heavy target atoms are identified by measuring the x-ray (L ? K) transitions in coincidence with projectiles undergoing charge exchange. The state selective cross sections for the population of the L-shell sub-levels of the projectile are determined, and in the case of excitation-ionization data compared to the detailed relativistic calculations. It is emphasized that the experimental data can serve as an important benchmark of the independent particle approximation and fully relativistic perturbative models, for the domain of relativistic ion-atom collisions.