In Cycle 1, you can specify up to 4 spectral windows (one per baseband), each with a different resolution and bandwidth if so desired. Selecting Spectral Line as Spectral Type will present you with the spectral window tables, as well as buttons to Select Lines to Observe, Add orDelete transitions. These actions must be performed individually for each baseband.
Adding a spectral window manually is straightforward: press the Add button and simply type the frequency (in the rest or sky frame) in the appropriate field in the table. Note that in contrast to the Continuum setup case the sky frequency as well as the rest frequency will adjust to account for the velocity of different sources; the value displayed in the spectral window table refers to the first source specified. Alternatively, you can Select Lines to Observe in baseband... from a catalogue. Pressing this button will bring up the Spectral Line Selector tool (see Fig. 3.4). Here, you can search an extensive database (the Splatalogue3.1) for popular transitions based on species, ALMA band, Sky frequency, maximum upper-state energy or molecules detected in a variety of astronomical sources. If you cannot find the transition you want in this offline database, try the Find More... button: you will then be able to search online from a more extensive database. Once you have identified the transition you are interested in, select it and press the Add to Selected Transitions button. You may add only one transition at a time, since the spectral window must be added individually for each baseband. The Hide unobservable lines option, ticked by default, allows you to display only transitions that are simultaneously observable with the transition(s) you have already selected for other basebands. When you press Ok, this will add a spectral window to the table with a centre frequency equal to the transition frequency. You will be able to verify all the transitions both in the baseband tables and visually in the spectral editor (see Fig. 3.5).
The OT will try to configure a spectral setup based on your input. In the spectral viewer, the sidebands are shaded in yellow and the spectral windows selected are indicated by the blue vertical (line frequency) and horizontal (bandwidth) lines. The latter are labelled according to the transition they refer to. If the OT cannot configure a valid spectral setup based on your input transitions, you will see a red error message in the Spectral Setup Errors box and in the spectral viewer the sidebands will be faded to grey rather than appearing in yellow. In order for your proposal to pass validation, you must select a valid spectral setup, where all spectral windows for all source velocities can fit within a valid sideband configuration. Note that for bands 3, 6 and 7 it is currently not possible to place 1 baseband in one sideband and 3 in the other, however 2 and 2 is acceptable, as is 4 spectral windows in one sideband. Band 9 has no such restrictions.
You can specify the bandwidth and spectral resolution (Hanning smoothed, corresponding to twice the channel spacing) of a spectral window by double-clicking on the Bandwidth, Resolution field in the spectral window tables, and choosing one of the options from the pull-down menu. If you increase the bandwidth you should ensure that the OT can configure a valid spectral setup. It is possible to change the centre frequency of spectral windows from the transition frequency in order to fit the spectral windows within the sideband, but please ensure that your lines are still covered by the spectral windows. Of course, if you cannot define a valid spectral setup for all the spectral windows you wish to observe, you can also put them into separate Science Goals.
Finally, you should carefully check the Representative Frequency displayed below the baseband tables and modify it if necessary (see previous section). For spectral line observations, the representative frequency should normally correspond to your transition of greatest interest, or if you are interested in several lines the one that has the poorest atmospheric transmission.