J/ApJ/849/5 L-edge single and multiple photoionization of Fe+ (Schippers+, 2017)
Near L-edge single and multiple photoionization of singly charged iron ions.
Schippers S., Martins M., Beerwerth R., Bari S., Holste K., Schubert K.,
Viefhaus J., Savin D.W., Fritzsche S., Muller A.
<Astrophys. J., 849, 5 (2017)>
=2017ApJ...849....5S 2017ApJ...849....5S
ADC_Keywords: Atomic physics
Keywords: atomic data; atomic processes; line: identification; line: profiles;
ISM: atoms; opacity
Abstract:
Absolute cross-sections for m-fold photoionization (m=1, ..., 6) of
Fe+ by a single photon were measured employing the photon-ion
merged-beams setup PIPE at the PETRA III synchrotron light source,
operated by DESY in Hamburg, Germany. Photon energies were in the
range 680-920eV, which covers the photoionization resonances
associated with 2p and 2s excitation to higher atomic shells as well
as the thresholds for 2p and 2s ionization. The corresponding
resonance positions were measured with an uncertainty of ±0.2eV. The
cross-section for Fe+ photoabsorption is derived as the sum of the
individually measured cross-sections for m-fold ionization.
Calculations of the Fe+ absorption cross-sections were carried out
using two different theoretical approaches, Hartree-Fock including
relativistic extensions and fully relativistic multiconfiguration
Dirac-Fock. Apart from overall energy shifts of up to about 3eV, the
theoretical cross-sections are in good agreement with each other and
with the experimental results. In addition, the complex de-excitation
cascades after the creation of inner-shell holes in the Fe+ ion were
tracked on the atomic fine-structure level. The corresponding
theoretical results for the product charge-state distributions are in
much better agreement with the experimental data than previously
published configuration-average results. The present experimental and
theoretical results are valuable for opacity calculations and are
expected to pave the way to a more accurate determination of the iron
abundance in the interstellar medium.
Description:
The present experiment on the photoionization of Fe+ ions was carried
out at the Photon-ion Spectrometer setup at PETRA III (PIPE; Figure
1). PETRA III is presently the brightest third-generation synchrotron
light source worldwide. It is operated by DESY in Hamburg, Germany.
The experimental arrangement and procedures have been described
previously (Schippers+ 2014JPhB...47k5602S 2014JPhB...47k5602S ; Mueller+ 2017ApJ...836..166M 2017ApJ...836..166M).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 157 1200 Measured cross sections
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See also:
J/A+AS/97/443 : Fluorescence for Be to Zn (Kaastra+ 1993)
J/A+AS/109/125 : Photoionisation cross section (Verner+, 1995)
J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)
J/ApJ/808/174 : FeII radiative transition rates (Bautista+, 2015)
J/ApJ/813/16 : Fe7+ ionization cross section (Hahn+, 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 eV E [680.9/921.1] Photon energy
9- 15 F7.5 Mbarn sig1 [0.008/2.6] Cross section for 1-fold
photoionization of Fe+ ions
17- 23 F7.5 Mbarn e_sig1 [0.003/0.02] Statistical experimental uncertainty
in sig1 (1)
25- 31 F7.5 Mbarn sig2 [0.1/3.3] Cross section for 2-fold
photoionization of Fe+ ions
33- 39 F7.5 Mbarn e_sig2 [0.001/0.02] Statistical experimental uncertainty
in sig2 (1)
41- 47 F7.5 Mbarn sig3 [0.03/4.7] Cross section for 3-fold
photoionization of Fe+ ions
49- 55 F7.5 Mbarn e_sig3 [0.001/0.02] Statistical experimental uncertainty
in sig3 (1)
57- 63 F7.5 Mbarn sig4 [0/0.6]? Cross section for 4-fold
photoionization of Fe+ ions
65- 75 E11.5 Mbarn e_sig4 [0/0.008]? Statistical experimental uncertainty
in sig4 (1)
77- 87 E11.5 Mbarn sig5 [0/0.1]? Cross section for 5-fold
photoionization of Fe+ ions
89- 99 E11.5 Mbarn e_sig5 [0/0.003]? Statistical experimental uncertainty
in sig5 (1)
101-112 E12.5 Mbarn sig6 [-3.3e-05/0.006] Cross section for 6-fold
photoionization of Fe+ ions
114-124 E11.5 Mbarn e_sig6 [1.4e-05/0.0004] Statistical experimental
uncertainty in sig6 (1)
126-133 F8.5 Mbarn sigT [0/11]? Total cross section for m-fold
photoionization of Fe+ ions
135-141 F7.5 Mbarn e_sigT [0/0.03]? Statistical experimental uncertainty
in sigT (1)
143-149 F7.5 --- q [0/4.3]? Mean product charge-state, Eq. 2, Fig. 8b
151-157 F7.5 --- e_q [0/0.03]? Statistical experimental uncertainty
in q
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Note (1): The systematic uncertainties of the energy and cross-section scales
are ±0.2eV and ±15% (at 90% confidence level), respectively.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Jun-2018