The first step to analyze our spectra is to select a spectral line
database. Weeds can access both the JPL database for molecular
spectroscopy and the Cologne Database for Molecular Spectroscopy
(CDMS). To select a database, type use in
, followed by the name
of the database2. For example:
[fontsize=\scriptsize] LAS90> use in cdms I-USE, cdms (online) selected
or:
[fontsize=\scriptsize] LAS90> use in jpl I-USE, jpl (online) selected
As mentioned already, Weeds makes online queries to the molecular databases. However, it is sometimes helpful to make offline searches in a database, for example if you are on travel with no (or a slow) internet connection. Weeds allows us to download a part of - or even the entire - spectral catalog from a database. This catalog is stored in a local database file, and can be used later for offline searches. Making a local copy of the CDMS database between 80 and 130 GHz is done as follows:
[fontsize=\scriptsize] LAS90> use in cdms I-USE, cdms (online) selected LAS90> use out mycdms.db LAS90> select /freq 80e3 130e3 I-SELECT, 128957 lines found in the frequency range 80000.0 to 130000.0 MHz LAS90> insert
Depending on the speed of your internet connection and the frequency range you have selected, making a local copy of a database may take from a few seconds to a few tens of minutes, so please be patient! In particular, copying the JPL database may take a while, because of technical limitations with this database; copying the CDMS database is much faster.
Once you have made a local copy of a database, you may select it with
the use in
command, followed by the name of the local database
file (.db
):
[fontsize=\scriptsize] LAS90> use in mycdms.db I-USE, mycdms.db (offline) selected
The use in
and use out
commands can be used to build a
local database containing lines from different sources (e.g. the CDMS
and the JPL), and even lines from a private catalog. See the online
documentation for more information.