### Abstract

We present R-matrix results for the electron-impact excitation of Fe6+. The intermediate-coupling frame transformation (ICFT) method has been used to obtain level-resolved collision strengths. We then calculate effective collision strengths assuming a Maxwellian distribution for the incident electron velocities. A large configuration interaction (CI) expansion of 1896 LS terms (4776 fine-structure levels) is used to obtain an accurate target. This is reduced to 89 close-coupling (CC) terms (189 levels) for the scattering calculation. To investigate the importance of CI, we also perform a second calculation with the same CC expansion but a smaller CI expansion. We discuss the difficulties of such a comparison and look at which transitions show the most sensitivity to the CI expansion. Our effective collision strengths are compared with a previous IRON Project report (Berrington et al. 2000, A&A, 142, 313) for transitions within the ground configuration and a recent distorted wave calculation (Zeng et al. 2005, MNRAS, 357, 440) for transitions to excited configurations. We find good agreement with the results of the previous R-matrix calculation and with the high-temperature distorted-wave results for most transitions, although there are some significant differences at lower temperatures in the latter case.

Original language | English |
---|---|

Pages (from-to) | 543-551 |

Number of pages | 8 |

Journal | Astronomy and Astrophysics |

Volume | 481 |

Issue number | 2 |

DOIs | |

Publication status | Published - Apr 2008 |

### Keywords

- atomic data
- intermediate-coupling frame transformation
- Maxwellian distribution
- configuration interaction

## Cite this

Witthoeft, M. C., & Badnell, N. R. (2008). Atomic data from the IRON Project LXV. Electron-impact excitation of Fe6+.

*Astronomy and Astrophysics*,*481*(2), 543-551. https://doi.org/10.1051/0004-6361:20079073