>6. The absorption spectrum calculated at the ground-state geometry >(optimized by RHF, MP2, DFT or state-specific CASSCF) should >correspond to the experimental absorption spectrum. As for the >emission, according to Kasha rule, emission occurs from the lowest >excited state (with only few exceptions). So, to obtain an emission >spectrum, you should always optimize S1 state. It is useful to turn on >state tracking option in order to see, whether state flipping occurs >during the optimization.
What if oscillator strength (at least with TDDFT) for the first excited state is zero? Still one needs to optimize to that state?