EGAS41 - Swansea University

41 st EGAS CP 21 Gdańsk 2009
Level shift and electron-impact excitation of H-like ions
in dense plasma
B. Li 1 , C.Z. Dong 1,∗ , J. Jiang 1
1 College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou
730070, China
∗ Corresponding author: dongcz@nwnu.edu.cn,
Plasma screening effect on atomic structures have been subject to extensive studied during
the last decades[1,2]. In the present work, the plasma effects on level shift and electronimpact
excitation (EIE) have been analyzed by including the Debye-Hückel potential into
the self-consistent Dirac-Fock equations. The wave functions of the target states are
generated by the modified package GRASP92[3]. Table 1 presents the level shift of H-like
Table 1: Level shift (eV) for Ar 17+ for different electron densities
n e (cm −3 ) 1s 2p 3p 4p
1×10 23 34.74 34.50 34.00 33.31
5×10 23 77.40 76.22 73.79 70.54
1×10 24 109.16 106.83 102.06 95.82
5×10 24 241.32 230.37 208.06 181.01
Ar 17+ ion in several electron densities for T e = 48 eV. Figure 1 show the total EIE cross
sections (a) and the magnetic sublevels EIE cross sections (b) of Lyman α 1 transition of
Ti 21+ . As a comparison, the theoretical results of Reed et al.[5] is also included in the
figure. For total cross section, from the figure we can see that our results are in very
good agreement with result of Reed et al. For excitation to the magnetic sublevels, it is
clear that the m = 0 sublevels is preferentially populated in electron-impact excitation.
However, for incident electron energies lower than 3 time of the theoreshold energy, there
is a significant discrepancy between the two results, this difference also result in a large
difference of polarization.
Cross section (10 -22 cm 2 )
4.5
4.0
3.5
3.0
2.5
2.0
1 2 3 4 5
Energy (threshold units)
(a)
Cross section (10 -22 cm 2 )
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
m=0.5
m=1.5
0.2
1 2 3 4 5
Energy (thershold units)
Figure 1: Total electron impact excitation cross sections (left) and magnetic sublevels cross
sections (right) of the 1s → 2p 3/2 of Ti 21+ . Solid line: theoretical values of Reed et al.[5], open
circles: DW calculations for free ion, open square: DW calculation at λ = 3, Diamond: open
square: DW calculation at λ = 1.5
References
[1] M.S. Murillo, J.C. Weisheit, Phys. Rep. 302,1 (1998)
[2] D. Salzman, Atomic Physics in Hot Plasma (Oxford Univ. Press, Oxford, 1998)
[3] F.A. Parpia et al., Comput. Phys. Commun. 94, 249 (1996)
[4] J. Jiang, C.Z. Dong, L.Y. Xie et al., Chin. Phys. Lett. 24, 691 (2007)
[5] K.J. Reed, M.H. Chen, Phys. Rev. A 48, 3644 (1993)
(b)
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