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<H2><A NAME="SECTION001164000000000000000">
Identification loop</A>
</H2>
<P>
The identification criterion combines estimate of the wavelength of a line
and an estimate of the error as well as a list laboratory wavelengths
to determine and guarantee the identification of a given line.
One could involve the additional knowledge of line strengths. But
in practice this information of limited use, in reason of variations
of relative line intensities caused by impurities, lamp ageing,
pressure variations, a.s.o. Accordingly, the identification criterion is:
<P>
<DIV ALIGN="CENTER">
<!-- MATH: $\lambda_c \equiv \lambda_{cat}$ -->
<IMG
WIDTH="46" HEIGHT="41" ALIGN="MIDDLE" BORDER="0"
SRC="img312.gif"
ALT="$ \lambda_c \equiv \lambda_{cat}$">
if <IMG
WIDTH="42" HEIGHT="56" ALIGN="BOTTOM" BORDER="0"
SRC="img313.gif"
ALT="$\exists$">!
<!-- MATH: $\lambda_{cat}$ -->
<IMG
WIDTH="66" HEIGHT="72" ALIGN="MIDDLE" BORDER="0"
SRC="img314.gif"
ALT="$\lambda_{cat}$">
/
<!-- MATH: $\parallel
\lambda_c - \lambda_{cat} \parallel <$ -->
<IMG
WIDTH="96" HEIGHT="42" ALIGN="MIDDLE" BORDER="0"
SRC="img315.gif"
ALT="$\parallel
\lambda_c - \lambda_{cat} \parallel <$">
<!-- MATH: $\delta\lambda$ -->
<IMG
WIDTH="54" HEIGHT="56" ALIGN="BOTTOM" BORDER="0"
SRC="img316.gif"
ALT="$\delta\lambda$"></DIV>
<P>
with <IMG
WIDTH="52" HEIGHT="72" ALIGN="MIDDLE" BORDER="0"
SRC="img317.gif"
ALT="$\lambda_c$">,
computed estimated wavelength,
<!-- MATH: $\lambda_{cat}$ -->
<IMG
WIDTH="66" HEIGHT="72" ALIGN="MIDDLE" BORDER="0"
SRC="img318.gif"
ALT="$\lambda_{cat}$">the catalog wavelength and
<!-- MATH: $\delta\lambda$ -->
<IMG
WIDTH="54" HEIGHT="56" ALIGN="BOTTOM" BORDER="0"
SRC="img319.gif"
ALT="$\delta\lambda$">,
a majorant of the error
of the computed wavelength, taken as the distance of the closest neighbor
in the line catalog or in the arc spectrum divided by a coefficient
<IMG
WIDTH="44" HEIGHT="54" ALIGN="BOTTOM" BORDER="0"
SRC="img320.gif"
ALT="$\alpha$">
which value does not exceed 1 (this parameter is controlled
by the session keyword <TT>WLCLOOP(2)</TT>).
<P>
<BR><HR>
<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-15</I>
</ADDRESS>
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