Resonance Interference and Absolute Cross Sections in Near-Threshold Electron-Impact Excitation of Multicharged Ions Page: 4 of 6
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20 e +Si2+ (3s2 1S) -+e +Si2+ (3s3p 3P)
N1 I
E 15
C,
o -
(-
. 10 .
o
Elcto Enry(V
2 g - - .
0
6.0 6.4 6.8 7.2 7.6
Electron Energy (eV)
Figure 2: Excitation cross sections for Si2+. The error bars are relative uncertainties at a
90% confidence level. The curves are convolutions of a Gaussian (0.24 eV FWHM) with
CCR calculations from Ref. 6 (solid) and Ref. 10 (dashed).
culty calculating the precise energies of the contributing resonances and their
interference. A similar situation exists for experimental cross sections 7 for the
4s2 15 - 4s4p 3P transition in Krs+. Guided by the measurements, Gorczyca
et al. refined their R-matrix calculations on Krs+ by including a Breit-Pauli
Hamiltonian to achieve fairly good agreement, although there remains a no-
ticeable discrepancy for one of the two measured resonance features.
Experimental excitation cross sections 9 for the 3s2 15 -+ 3s3p 3P transi-
tion in Si2+ are also dominated by a dielectronic resonance, with a measured
cross section of about 16 x 10-16 cm2 just above threshold, in excellent agree-
ment with two separate CCR calculations 6'0 as shown in Fig. 2. Ion energy
limitations prevented measurements beyond 7.6 eV in the range of a second
predicted6"0 resonance peak. Measured cross sections for the optically-allowed
3s2 1S -+ 3s3p 1P transition in Si2+ are in fair agreement with the CCR cal-
culations, with the experimental data showing a sharper drop from the peak3
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Bannister, M. E.; Chung, Y. S.; Djuric, N.; Wallbank, B.; Woitke, O.; Zhou, S. et al. Resonance Interference and Absolute Cross Sections in Near-Threshold Electron-Impact Excitation of Multicharged Ions, article, December 31, 1997; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc690919/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.