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