The ptSS-PCM procedure described in Section II C has previous been implemented for CI wave functions with single excitations only (i.e., CIS), which is technically simpler because in that case the reference state is the physical ground state. In this context timedependent (TD-) DFT can be considered another CIStype method, and TD-DFT + ptSS-PCM was also implemented in previous work. The latter approach is very similar to the "corrected linear response theory" of Caricato et al..