A large-scale R-matrix calculation for electron-impact excitation of the Ne2 +, O-like ion

B M Mclaughlin (1, 2) , Teck-Ghee Lee (3) , J A Ludlow (3) , E Landi (4) , S D Loch (3) , M S Pindzola (3) , C P Ballance (3)

1 School of Mathematics and Physics
2 ITAMP - Institute for Theoretical Atomic, Molecular and Optical Physics [Cambridge]
3 Department of Physics [Auburn]
4 AOSS - Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor]

The five JΠ levels within a np2 or np4 ground state complex provide an excellent testing ground for the comparison of theoretical line ratios with astrophysically observed values, in addition to providing valuable electron temperature and density diagnostics. The low temperature nature of the line ratios ensure that the theoretically derived values are sensitive to the underlying atomic structure and electron-impact excitation rates. Previous R- matrix calculations for the O-like Ne ion, Ne2+, exhibit spurious structure in the cross sections at higher electron energies, which may effect Maxwellian averaged rates even at low temperatures. Furthermore, there is an absence of comprehensive excitation data between the excited states that may provide newer diagnostics to compliment the more established lines discussed in this paper. To resolve these issues, we present both a small-scale 56-level Breit-Pauli (BP) calculation and a large-scale 554 levels R-matrix Intermediate Coupling Frame Transformation (ICFT) calculation that extends the scope and validity of earlier JAJOM calculations both in terms of the atomic structure and scattering cross sections. Our results provide a comprehensive electron-impact excitation data set for all transitions to higher n− shells. The fundamental atomic data for this O-like ion is subsequently used within a collisional radiative framework to provide the intensity line ratios across a range of electron temperatures and densities of interest in astrophysical observations.

Mots clés: Physical Sciences

B M Mclaughlin, Teck-Ghee Lee, J A Ludlow, E Landi, S D Loch, et al.. A large-scale R-matrix calculation for electron-impact excitation of the Ne2 +, O-like ion. Journal of Physics B: Atomic, Molecular and Optical Physics, 2011, 44 (17), pp.175206. ⟨10.1088/0953-4075/44/17/175206⟩. ⟨hal-00651653⟩