I did an excited state calculation (TD-SCF)in Gaussian and wanted to see the MOs of the first excited state. But when I opened the checkpoint file in GaussView5 and clicked edit -> MOs, I could only see the configuration and MOs of the ground state. How do I see the excited state MOs in GaussView or other visualisers that can be downloaded for free?
What you see, when you open your checkpoint file, is all you can see. I assume you use TDDFT and with this method you can't obtain other orbitals than the ones from the ground state. Why is this so?
Because in LR-TDDFT you calculate your ground state and apply a perturbation to it. (You can look up on the behind theory in good books like Introduction to Computational Chemistry from Frank Jensen.) The result from this calculation is presented from Gaussian like this:
Excited State 1: Singlet-A 1.0662 eV 1162.87 nm f=0.0007 <S**2>=0.000 110 ->113 0.60155 (0.72) 110 ->115 -0.23139 (0.11) 110 ->116 0.22569 (0.10) Excited State 2: Singlet-A 1.2549 eV 988.02 nm f=0.0002 <S**2>=0.000 109 ->113 -0.39288 (0.31) 110 ->114 0.51726 (0.54) Excited State 3: Singlet-A 1.2929 eV 958.99 nm f=0.0027 <S**2>=0.000 109 ->113 0.50172 (0.50) 110 ->114 0.29522 (0.17) (The weights in spaces are added by me.)
These are the configurations of three excited states. The first excited state, for example, consists mainly (72%) from an excitation from MO 110 (HOMO) to MO 113 (LUMO+2). There are some contributions with weights of about 10% into the MOs 115 and 116. (On how to get the weights, have a look at an answer by me on this site here.)
You ask, how you can see the excited state in GaussView. You can't ... directly. And this question is also a little bit tricky, because what is it that you want to see? Here are some options:
calculate the electron density of the excited state
TD(Root=1) Density(Current)and subtract the electron density from the ground state. Then this difference shows you the "hole" where now is less density and the "hole" where there is more density.
calculate Charge Density Differences (CDD) with Multiwfn or Electronic Difference Density Maps (EDDM) with GaussSum which show you the same but a little bit easier as you do not need an additional calculation because they are based on the excitations and the CI coefficients.
calculate the transition density for the excited state
calculate Natural Transition Orbitals with, e.g., Gaussian or Multiwfn, for very diffuse excitated states as NTOs reduces/optimizes the number of contributing excitations for each root with