Fully relativistic R -matrix calculation of electron impact excitation of NeIX
Abstract
We report on a fully relativistic close-coupling (CC) calculation of the electron impact excitation (EIE) of NeIX . The multiconfiguration Dirac-Fock (MCDF) method was used in a calculation of NeIX atomic structure. The EIE calculation of NeIX was carried out using the Dirac R -matrix method and the MCDF orbitals for principal quantum number n≤5 with target states up to n=5 corresponding to 49CC (49 target states in the CC expansion). The EIE calculation included both resonance and channel coupling effects. We demonstrate that strong resonances appear in the excitation of the highly charged ion NeIX , in particular for intercombination and forbidden transitions. Compared to less highly charged He-like ions, we show that for NeIX all N -shell and O -shell levels start to give rise to Rydberg resonant states dipping just below M -shell and N -shell target thresholds, respectively. In comparison with previous calculations carried out with either the close-coupling or the distorted wave method, our calculations show significant differences with respect to cross sections and effective collision strengths. The important NeIX line intensity G ratio (G=(i+f)/r)=[forbidden+intercombination]/resonance) calculated based on our MCDF and Dirac R -matrix results is in good agreement with the existing accurate EBIT measurements. This calculation has direct applications to laboratory measurements and observations of astrophysical x-ray sources.
- Publication:
-
Physical Review A
- Pub Date:
- October 2006
- DOI:
- 10.1103/PhysRevA.74.042709
- Bibcode:
- 2006PhRvA..74d2709C
- Keywords:
-
- 34.80.Kw;
- 95.30.Ky;
- 52.70.La;
- Electron-ion scattering;
- excitation and ionization;
- Atomic and molecular data spectra and spectral parameters;
- X-ray and gamma-ray measurements