It was so helpful for me.

I have an additional question.
I understood the way to calculate the vertical transition energies.
My question is that

Which function should I use to analyze the energy difference between ground and excited state in an adiabatic way?
I mean the way to compare the two energy states in the multiwfn program.

Thank you for your kindness.

Vertical excitation energies can be directly loaded from output file of your quantum chemistry program. If you are using Gaussian, ORCA, sTDA, Multiwfn is also able to directly print all excitation energies. For example, boot up Multiwfn and input:
examples\excit\4-nitroaniline.out  // Output file of TDDFT task of Gaussian
11  // Plot spectrum
3  // UV-Vis
-1  // Show transition data

Now you can see

Index  Excit.energy(eV       nm        1000 cm^-1)       Oscil.str
   1         4.05570      305.70358       32.71143        0.00000
   2         4.27620      289.94013       34.48988        0.33720
   3         4.58460      270.43624       36.97730        0.00010

Since the geometry used in this calculation is the optimized ground state geometry, therefore these excitation energies correspond to vertical excitation energies.

If you need to obtain adiabatic excitation energy, you should optimize both ground state and excited state. The difference between the excited state energy at optimized excited state geometry and the ground state energy at optimized ground state geometry is simply adiabatic excitation energy.

First of all, I want to thank you for making a great program. It was very helpful in my research works.
I am really appreciative of you, sir.

Now, I am trying to analyze some excited states of organic materials.
I wonder whether the multiwfn program can show excited state energies or not.
I would like to calculate some excited energies of singlets and triplets.
My questions are that

1. How can I get the vertical transition energy from the ground state to excited states (S1, T1, ...)?
2. How can I get the adiabatic transition energy from the ground state to excited states?

I will wait for your reply.
Thank you.