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Fig. 1 show an example scan from a spectral
survey. Spectral surveys typically have many different scans of this
kind, each corresponding to a different frequency setting. The scan on
the figure show several well detected lines that we want to
identify. This can be done with lid
which allow us to select a
line on the scan with the mouse. Clicking on the left button of the
mouse over some part of the spectrum selects a line. Then the command
searches in the database (which has been selected previously with the
dbselect
command, as explained above) for lines within 1 MHz of
the selected region(s) of the spectrum. For each line found, the
command mark the rest frequency of the line on the scan, and a table
displaying the line frequency, upper level energy, Einstein
coefficient and quantum numbers and is printed:
[fontsize=\footnotesize] LAS90> lid -------------------------------------------------------------------------------------------- | Species | Freq. (GHz) | Eup (K) | Aul (s-1) | Upper level -- Lower level | -------------------------------------------------------------------------------------------- | CH3OH, vt=0,1 | 96.739362 | 12.5 | 2.56e-06 | 2 -1 2 0 -- 1 -1 1 0 | --------------------------------------------------------------------------------------------
Most of the time, several line candidates are found for a given
frequency. For example, using lid
to search for lines in the
catalog around the brightest line in Fig. 1,
we obtain:
[fontsize=\footnotesize] LAS90> lid -------------------------------------------------------------------------------------------- | Species | Freq. (GHz) | Eup (K) | Aul (s-1) | Upper level -- Lower level | -------------------------------------------------------------------------------------------- | n-C3H7CN | 96.741208 | 158.0 | 7.60e-06 | 12 310 1 -- 11 2 9 1 | | C4H, v7=1 | 96.741314 | 214.2 | 3.74e-06 | 10 111 -- 9-110 | | CH3OH, vt=0,1 | 96.741375 | 7.0 | 3.41e-06 | 2 0 2 +0 -- 1 0 1 +0 | --------------------------------------------------------------------------------------------
Searches in the database may be refined to lines with an upper level
energy lower than a given value using the /energy
option, or to
lines with an Einstein coefficient greater than a given value with the
/aeinstein
option. The /species
option allow to restrict
searches to a given species.
It should be noted lid
prints the line upper and lower level
quantum numbers exactly as they appear in the selected database. We
refer the user to the documentation of these databases for the meaning
of these quantum numbers.