SIMBAD references

Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [FeII] transitions that are observed as strong features in astrophysical spectra. We measure lifetimes for the 3d⁶(³G)4sa⁴G_11/2 and 3d⁶(³D)4sb⁴D_1/2 metastable levels in FeII and experimental transition probabilities for the forbidden transitions 3d⁷a⁴F_7/2,9/2-3d⁶(³G)4sa⁴G_11/2. The lifetimes were measured at the ion storage ring facility CRYRING using a laser probing technique. Astrophysical branching fractions were obtained from spectra of Eta Carinae, obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The lifetimes and branching fractions were combined to yield absolute transition probabilities. The lifetimes of the a⁴G_11/2 and the b⁴D_1/2 levels have been measured and have the following values, τ=0.75±0.10s and τ=0.54±0.03s respectively. Furthermore, we have determined the transition probabilities for two forbidden transitions of a⁴F_7/2,9/2-a⁴G_11/2 at 4243.97 and 4346.85Å. Both the lifetimes and the transition probabilities are compared to calculated values in the literature.