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3. Results

We measure 7 of the VUV lines of the tex2html_wrap_inline857 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 tex2html_wrap_inline861 relative to both tex2html_wrap_inline863 and tex2html_wrap_inline865. The results are: f (tex2html_wrap_inline869) / f (tex2html_wrap_inline873 and f (tex2html_wrap_inline877) / f (tex2html_wrap_inline881. From previous work (Bergeson et al. 1996a), we know f (tex2html_wrap_inline885) / f (tex2html_wrap_inline889. We can verify that our VUV work agrees with this as well: tex2html_wrap_inline891 (tex2html_wrap_inline893) / f (tex2html_wrap_inline897 / tex2html_wrap_inline899 (tex2html_wrap_inline901) / f (tex2html_wrap_inline905. 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 tex2html_wrap_inline909 multiplet of Fe II. The 2 weakest lines in the multiplet at tex2html_wrap_inline911 and tex2html_wrap_inline913 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 tex2html_wrap_inline919 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).

 table278
Table 2: Absolute VUV absorption oscillator strengths compared to values in the literature


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