Line Catalog
============

The built-in line catalog currently includes the following transitions.

CO Family
---------

- ``12CO(1-0)``
- ``12CO(2-1)``
- ``12CO(3-2)``
- ``12CO(4-3)``
- ``12CO(6-5)``
- ``12CO(7-6)``
- ``13CO(1-0)``
- ``13CO(2-1)``
- ``13CO(3-2)``
- ``13CO(4-3)``
- ``C18O(1-0)``
- ``C18O(2-1)``
- ``C18O(3-2)``
- ``C18O(4-3)``
- ``C17O(1-0)``
- ``C17O(2-1)``
- ``C17O(3-2)``

Dense Gas Tracers
-----------------

- ``HCN(1-0)``
- ``HCN(3-2)``
- ``HCN(4-3)``
- ``HCO+(1-0)``
- ``HCO+(3-2)``
- ``HCO+(4-3)``
- ``HNC(1-0)``
- ``HNC(3-2)``
- ``HNC(4-3)``
- ``N2H+(1-0)``
- ``N2H+(3-2)``
- ``CS(2-1)``
- ``CS(3-2)``
- ``CS(5-4)``
- ``CS(7-6)``

PDR and Diffuse-Gas Tracers
---------------------------

- ``CN(1-0)``
- ``CN(2-1)``
- ``CCH(1-0)``
- ``CCH(3-2)``

Atomic Carbon
-------------

- ``[CI](1-0)``
- ``[CI](2-1)``

Shock Tracers
-------------

- ``SiO(2-1)``
- ``SiO(5-4)``
- ``SiO(8-7)``
- ``SO(5_6-4_5)``
- ``SO(6_5-5_4)``
- ``SO2(11_1,11-10_0,10)``

Chemistry and Cold Gas
----------------------

- ``H2CO(3_03-2_02)``
- ``H2CO(3_22-2_21)``
- ``H2CO(3_21-2_20)``
- ``H2CO(2_12-1_11)``
- ``NH2D(1_11-1_01)``

Complex and Star-Forming Tracers
--------------------------------

- ``CH3OH(5_0-4_0)``
- ``CH3OH(2_k-1_k)``
- ``CH3CN(12_0-11_0)``

Recombination Lines
-------------------

- ``H30alpha``
- ``H40alpha``

Notes
-----

Some entries such as ``CN``, ``CCH``, and ``CH3OH(2_k-1_k)`` are practical
group-center proxies for blended or multi-component spectral complexes.