1,766 research outputs found
Analytical expression for the convolution of a Fano line profile with a Gaussian
Asymmetric Fano line profiles are frequently encountered, e.g., in the
photoionization spectra of atoms and ions. For the fitting of spectral line
profiles to experimental spectra the line profiles have to be convolved with
the experimental window function. The latter is often taken to be a Gaussian.
It is shown that the convolution can be represented by a rather simple analytic
expression involving the Faddeeva function for the evaluation of which
efficient and accurate numerical algorithms are available.Comment: Refined version, old figure removed, new figure, new references,
expanded discussion, accepted for publication by the Journal of Quantitative
Spectroscopy and Radiative Transfe
Interference effects in the photorecombination of argonlike Sc3+ ions: Storage-ring experiment and theory
Absolute total electron-ion recombination rate coefficients of argonlike
Sc3+(3s2 3p6) ions have been measured for relative energies between electrons
and ions ranging from 0 to 45 eV. This energy range comprises all dielectronic
recombination resonances attached to 3p -> 3d and 3p -> 4s excitations. A broad
resonance with an experimental width of 0.89 +- 0.07 eV due to the 3p5 3d2 2F
intermediate state is found at 12.31 +- 0.03 eV with a small experimental
evidence for an asymmetric line shape. From R-Matrix and perturbative
calculations we infer that the asymmetric line shape may not only be due to
quantum mechanical interference between direct and resonant recombination
channels as predicted by Gorczyca et al. [Phys. Rev. A 56, 4742 (1997)], but
may partly also be due to the interaction with an adjacent overlapping DR
resonance of the same symmetry. The overall agreement between theory and
experiment is poor. Differences between our experimental and our theoretical
resonance positions are as large as 1.4 eV. This illustrates the difficulty to
accurately describe the structure of an atomic system with an open 3d-shell
with state-of-the-art theoretical methods. Furthermore, we find that a
relativistic theoretical treatment of the system under study is mandatory since
the existence of experimentally observed strong 3p5 3d2 2D and 3p5 3d 4s 2D
resonances can only be explained when calculations beyond LS-coupling are
carried out.Comment: 11 pages, 7 figures, 3 tables, Phys. Rev. A (in print), see also:
http://www.strz.uni-giessen.de/~k
Dielectronic recombination data for astrophysical applications: Plasma rate-coefficients for Fe^q+ (q=7-10, 13-22) and Ni^25+ ions from storage-ring experiments
This review summarizes the present status of an ongoing experimental effort
to provide reliable rate coefficients for dielectronic recombination of highly
charged iron ions for the modeling of astrophysical and other plasmas. The
experimental work has been carried out over more than a decade at the heavy-ion
storage-ring TSR of the Max-Planck-Institute for Nuclear Physics in Heidelberg,
Germany. The experimental and data reduction procedures are outlined. The role
of previously disregarded processes such as fine-structure core excitations and
trielectronic recombination is highlighted. Plasma rate coefficients for
dielectronic recombination of Fe^q+ ions (q=7-10, 13-22) and Ni^25+ are
presented graphically and in a simple parameterized form allowing for easy use
in plasma modeling codes. It is concluded that storage-ring experiments are
presently the only source for reliable low-temperature dielectronic
recombination rate-coefficients of complex ions.Comment: submitted for publication in the International Review of Atomic and
Molecular Physics, 8 figures, 3 tables, 68 reference
Enhanced dielectronic recombination of lithium-like Ti19+ ions in external ExB fields
Dielectronic recombination(DR) of lithium-like Ti19+(1s2 2s) ions via 2s->2p
core excitations has been measured at the Heidelberg heavy ion storage ring
TSR. We find that not only external electric fields (0 <= Ey <= 280 V/cm) but
also crossed magnetic fields (30 mT <= Bz <= 80 mT) influence the DR via high-n
(2p_j nl)-Rydberg resonances. This result confirms our previous finding for
isoelectronic Cl14+ ions [Bartsch T et al, PRL 82, 3779 (1999)] that
experimentally established the sensitivity of DR to ExB fields. In the present
investigation the larger 2p_{1/2}-2p_{3/2} fine structure splitting of Ti19+
allowed us to study separately the influence of external fields via the two
series of Rydberg DR resonances attached to the 2s -> 2p_{1/2} and 2s ->
2p_{3/2} excitations of the Li-like core, extracting initial slopes and
saturation fields of the enhancement. We find that for Ey > 80 V/cm the field
induced enhancement is about 1.8 times stronger for the 2p_{3/2} series than
for the 2p_{1/2} series.Comment: 10 pages, 3 figures, to be published in Journal of Physics B, see
also http://www.strz.uni-giessen.de/~k
Productive organizational energy mediates the impact of organizational structure on absorptive capacity
The ability of an organization to cope with radical technological change is regarded to be heavily dependent on its ability to absorb and apply knowledge from its environment. This study investigates the role of organizational structure in driving absorptive capacity and uncovers the role of the emergent phenomenon of organizational energy as the enabler of this relationship. A field study was conducted among firms that are challenged by the disruptive nature of Cloud computing. Our results show that organizational design affects the degree of mobilization of an organization's affective, cognitive and behavioral resources, which in turn influence the effectiveness of learning processes related to the absorption and exchange of knowledge within the organization. Furthermore, they reveal the positive relationship between the enactment of absorptive capacity and the successful adoption of Cloud technology for incumbent firms. The findings contribute to our understanding of the micro-foundations of absorptive capacity and how positive organizational phenomena facilitate effective adoption and implementation of emerging technologies
Photoionization of tungsten ions: experiment and theory for W
Experimental and theoretical results are reported for single-photon single
ionization of the tungsten ion W. Absolute cross sections have been
measured employing the photon-ion merged-beams setup at the Advanced Light
Source in Berkeley. Detailed photon-energy scans were performed at 200~meV
bandwidth in the 40 -- 105~eV range. Theoretical results have been obtained
from a Dirac-Coulomb R-matrix approach employing basis sets of 730 levels for
the photoionization of W. Calculations were carried out for the
, =2, ground level and the
associated fine-structure levels with =3 and 4 for the W ions. In
addition, cross sections have been calculated for the metastable levels
. Very satisfying agreement of theory and experiment is
found for the photoionization cross section of W which is remarkable
given the complexity of the electronic structure of tungsten ions in low charge
states.Comment: 15 pages, 3 figures, to appear in the Journal of Physics B: Atomic,
Molecular and Optical Physic
Near--K-edge double and triple detachment of the F- negative ion: observation of direct two-electron ejection by a single photon
Double and triple detachment of the F-(1s2 2s2 2p6) negative ion by a single
photon have been investigated in the photon energy range 660 to 1000 eV. The
experimental data provide unambiguous evidence for the dominant role of direct
photo-double-detachment with a subsequent single-Auger process in the reaction
channel leading to F2+ product ions. Absolute cross sections were determined
for the direct removal of a (1s+2p) pair of electrons from F- by the absorption
of a single photon
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