We measure 7 of the VUV lines of the multiplet (#8) of Fe II; each of the 7 VUV lines is measured relative to two different UV transitions. This provides us with an internal consistency check for our data since we know accurate absorption f-values for all of the UV transitions of Fe II used as reference lines in this experiment. For example, we measure the transition at relative to both and . The results are: f () / f ( and f () / f (. From previous work (Bergeson et al. 1996a), we know f () / f (. We can verify that our VUV work agrees with this as well: () / f ( / () / f (. This cross-check allows us to identify inconsistencies in our data set.
Table 2 lists the absorption f-values for 7 of the VUV transitions from the ground term to the multiplet of Fe II. The 2 weakest lines in the multiplet at and are not included in Table 2 because the data quality was unsatisfactory. Energy levels in Table 2 are from Johansson (1978). The absorption f-values are accurate to typically 10%. This accuracy is limited in part by the uncertainty on the primary UV reference lines as discussed in the Introduction. The somewhat larger uncertainty on the f-value of the line at is due to larger photon statistical noise. This particular line is far from the blaze angle of the echelle grating. The f-values are compared to the theoretical results of Kurucz (1988), Fawcett (1988), and Nussbaumer et al. (1981) as well as to the observational results of Cardelli & Savage (1995) and Shull et al. (1983).
Table 2: Absolute VUV absorption oscillator strengths compared to values in the literature