If the purpose of a calculation is to predict the energy of photoexcitation,
then the ground-state should first be optimized. Once this is done, then a
C.I. calculation can be carried out using 1SCF. With the appropriate
keywords (MECI C.I.=n etc.), the energy of photoexcitation to the
various states can be predicted.
A more expensive, but more rigorous, calculation would be to optimize the
geometry using all the C.I. keywords. This is unlikely to change the results
significantly, however.