Query related to CVS_EE_SINGLETS in FC-CVS-EOM-EE-CCSD calculation

Hi
I am trying to do the XAS calculations using FC-CVS-EOM-EE-CCSD method and I got the input example provided in the manual.
But I do not understand what are the numbers in CVS_EE_SINGLETS ([3,0,2,1] in the example)
I understand that its number of excited states in different irrep but how do we decide how many irrep (like 4 here) we have and how to select the numbers?

And also for open shell molecules, what will be the changes required to compute the XAS other than multiplicity of the molecule?

Hello. Can anyone please help in this regard?

Depends on the point group that QChem assigns to your molecule. If it finds the molecule to be Cs then look up the table of irreps for Cs online. As to how each irrep is assigned to the list, I remember reading it somewhere in the manual at some point but couldnt find it.

For open shell molecules use CVS_EE_STATES instead of CVS_EE_SINGLETS or CVS_EE_TRIPLETS. Unless they are core → SOMO transitions, they’ll likely be strongly spin contaminated.