J/ApJ/760/80 Fe9+ and Fe10+ cross-section measurements (Hahn+, 2012)
Storage ring cross-section measurements for electron impact single and double
ionization of Fe9+ and single ionization of Fe10+.
Hahn M., Becker A., Grieser M., Krantz C., Lestinsky M., Muller A.,
Novotny O., Repnow R., Schippers S., Spruck K., Wolf A., Savin D.W.
<Astrophys. J., 760, 80 (2012)>
=2012ApJ...760...80H 2012ApJ...760...80H
ADC_Keywords: Atomic physics
Keywords: atomic data; atomic processes
Abstract:
We have measured electron impact ionization from the ground state of
Fe9+ and Fe10+ over the relative electron-ion collision energy
ranges 200-1900eV and 250-1800eV, respectively. The ions were confined
in an ion storage ring long enough for essentially all metastable
levels to radiatively relax to the ground state. For single
ionization, we find a number of discrepancies between the existing
theoretical cross sections and our results. The calculations appear
to neglect some excitation-autoionization (EA) channels, particularly
from n=3 to n' excitations, which are important near threshold, and
those from n=2-->3 excitations, which contribute at about 650eV.
Conversely, at higher energies the calculations appear to overestimate
the importance of EA channels due to excitation into levels where
n≥4. The resulting experimental rate coefficients agree with the most
recent theory for Fe9+ to within 16% and for Fe10+ to within 19%
at temperatures where these ions are predicted to form in collisional
ionization equilibrium. We have also measured double ionization of
Fe9+ forming Fe11+ in the energy range 450-3000eV and found that
although there is an appreciable cross section for direct double
ionization, the dominant mechanism appears to be through direct
ionization of an inner shell electron producing an excited state that
subsequently stabilizes through autoionization.
Description:
Measurements were carried out using the TSR heavy ion storage ring at
the Max-Planck-Institut fur Kernphysik in Heidelberg, Germany.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 29 340 Fe9+ single ionization cross section
(e-+Fe9+ -> Fe10++2e-)
table3.dat 29 318 Fe10+ single ionization cross section
(e-+Fe10+ -> Fe11++2e-)
table5.dat 29 256 Fe9+ double ionization cross section
(e-+Fe9+ -> Fe11++3e-)
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See also:
J/A+A/565/A77 : Atomic data for FeIX (Del Zanna+, 2014)
J/A+A/537/A22 : Atomic data for X-ray lines of FeVIII & FeIX (O'Dwyer+, 2012)
J/ApJ/740/L52 : FeIX energy levels (Foster+, 2011)
J/A+A/466/771 : H to Zn ionization rate coefficients (Dere+, 2007)
J/A+AS/133/403 : Ionization balance for optically thin plasmas (Mazzotta+ 1998)
J/A+AS/97/443 : Fluorescence for Be to Zn (Kaastra+ 1993)
Byte-by-byte Description of file: table[235].dat
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Bytes Format Units Label Explanations
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1- 6 F6.1 eV E [205/3000] Collision energy
8- 18 E11.4 cm2 sigma Ionization cross section σI
20- 29 E10.4 cm2 e_sigma Statistical uncertainty in σI
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Jul-2014