scholarly journals Fe XIII Emission Lines Observed by EUVE and the S082A Instrument On-Board Skylab

1996 ◽  
Vol 152 ◽  
pp. 525-529
Author(s):  
F.P. Keenan ◽  
J.J. Drake ◽  
V.J. Foster ◽  
C.J. Greer ◽  
S.S. Tayal ◽  
...  
Keyword(s):  
Electron Density ◽  
Extreme Ultraviolet ◽  
Emission Lines ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Naval Research ◽  
R Matrix ◽  
Measured Line ◽  
Good Agreement

Recent R-matrix calculations of electron impact excitation rates for Fe XIII are used to derive the theoretical electron density sensitive emission line ratios R1 = I(318.12 Å)/I(320.80 Å) and R2 = I(256.42 Å)/I(251.95 Å), which are found to be up to 50% different from earlier diagnostics. A comparison of the current line ratios with both solar flare and active region observations, obtained by the Naval Research Laboratory’s S082A spectrograph on board Skylab, reveals generally good agreement between densities deduced from Fe XIII and those estimated from diagnostic line ratios in species formed at similar temperatures. This provides experimental support for the accuracy of the line ratio calculations, and hence the atomic data adopted in their derivation. In Extreme Ultraviolet Explorer satellite (EUVE) spectra the Fe XIII emission lines are found to be severely blended. However, an analysis of these lines measured in the spectra of Procyon and α Cen demonstrates that they still allow very approximate values of the electron density to be inferred. Moreover, it should be possible to increase the accuracy of the measured line fluxes, and hence of the inferred densities, if longer exposures of the stars concerned can be obtained.

scholarly journals R-Matrix Scattering Calculations for Iron-Peak Species: Photoionisation of Fe I and Electron-Impact Excitation of Fe II

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 87 ◽  
Author(s):  
Ryan Smyth ◽  
Catherine Ramsbottom ◽  
Connor Ballance
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Emission Lines ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
High Quality ◽  
Matrix Methods ◽  
R Matrix ◽  
Astrophysical Objects

An abundance of absorption and emission lines of iron-peak species such as Fe I and Fe II can be seen in the spectra of many astrophysical objects. Thus, the accurate modelling of such spectra requires sets of high quality atomic data for these species. In this paper, we present preliminary results from the present electron-impact excitation calculations for Fe II and fine-structure resolved photoionisation calculations for Fe I employing the Dirac atomic R-matrix and Breit–Pauli R-matrix methods. For the Fe II excitation, we compare results with all existing calculations, and for the Fe I photoionisation, we present a sample of level-resolved cross-sections. The calculations and results described throughout will be of use to those requiring high quality atomic data for modelling a wide variety of astrophysical objects.

scholarly journals S II emission lines in Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 258-258
Author(s):  
F.C. McKenna ◽  
F. P. Keenan ◽  
L. H. Aller ◽  
S. Hyung ◽  
K. L. Bell ◽  
...  
Keyword(s):  
Electron Impact ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data

Emission lines arising from transitions in S II have been detected in a wide variety of astronomical sources, including planetary nebulae (Hyung, Keyes & Aller 1995). These transitions are used to derive information on emitting plasmas parameters (Te, Ne) through diagnostic line ratios, although to calculate these quantities reliably, accurate atomic data must be employed, especially for electron impact excitation rates.

Recent Radiative and Collisional Atomic Data of Astrophysical Interest

1988 ◽  
Vol 102 ◽  
pp. 129-132
Author(s):  
K.L. Baluja ◽  
K. Butler ◽  
J. Le Bourlot ◽  
C.J. Zeippen
Keyword(s):  
Mass Production ◽  
Bound States ◽  
Physical Models ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Isoelectronic Sequence ◽  
Astrophysical Interest ◽  
Radiative Transitions ◽  
Forbidden Transitions

SummaryUsing sophisticated computer programs and elaborate physical models, accurate radiative and collisional atomic data of astrophysical interest have been or are being calculated. The cases treated include radiative transitions between bound states in the 2p4and 2s2p5configurations of many ions in the oxygen isoelectronic sequence, the photoionisation of the ground state of neutral iron, the electron impact excitation of the fine-structure forbidden transitions within the 3p3ground configuration of CℓIII, Ar IV and K V, and the mass-production of radiative data for ions in the oxygen and fluorine isoelectronic sequences, as part of the international Opacity Project.

scholarly journals Electron-impact double ionization of the carbon atom

2018 ◽  
Vol 620 ◽  
pp. A188 ◽  
Author(s):  
Valdas Jonauskas
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Cross Sections ◽  
Double Ionization ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Ionization Cross ◽  
Ionization Cross Sections ◽  
Good Agreement

Electron-impact single- and double-ionization cross sections and Maxwellian rate coefficients are presented for the carbon atom. Scaling factors are introduced for the electron-impact excitation and ionization cross sections obtained in the distorted wave (DW) approximation. It is shown that the scaled DW cross sections provide good agreement with measurements for the single ionization of the C atom and C1+ ion. The direct double-ionization (DDI) process is studied using a multi-step approach. Ionization–ionization, excitation–ionization–ionization, and ionization–excitation–ionization branches are analyzed. It is demonstrated that the three-step processes contribute ≼40% of the total DDI cross sections for the case where one of the electrons takes all of the excess energy after the first ionization process.

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