interpretation of ccsd excited state

[kaushikhatua]

Hi all
I have carried out a excited state calculation within ccsd formalism of lowest 5 electronic excited states. Lowest energy transition has been determined by oscillator strength. To see the dominant orbitals involved in virtual transition I check the output files where maximum amplitude corresponds to transition between HOMO and some inner orbitals. I don't understand how transition occurs in such a orbital which is already occupied. Any help or interpretation of ccsd excited state calculations will be appreciated.