companying calculations it was found that excited states could be delocalized across the ion pair in some cases, such that the computational modeling should not be limited to the individual cations and anions. Spectra shown in Fig. for one particular structure of [C 4 C 1 Im][SCN] were computed at the SRC1-r1/ 6-311(2+,2+)G(d,p) level of theory, mirroring LR-TDDFT/CVS calculations reported previously. Absent the filtering step, the TDKS spectrum is simply uninterpretable as there is significant contamination from C(1s) → continuum excitations. Interloper states contribute spurious (albeit high-intensity) pre-edge features but also overlap with the nitrogen K-edge itself. Upon filtering, a good match is obtained to LR-TDDFT/CVS results, with the nitrogen K-edge appearing at 387.5 eV with a second peak at 389.4 eV. Experimentally, these two features appear at 399.5 eV and 401.9 eV (although they are quite broad), so the spectra in Fig. must be shifted by about 12 eV to match. However, the chemical shift between the two peaks is predicted more accurately: 1.9 eV (theory) versus 2.4 eV (experiment). Note that the [C 4 C 1 Im][SCN] dimer exhibits conformationdependent spectral shifts up to ∼ 1 eV, and we have not attempted any conformational search here. The filtered TDKS spectrum is a good match to the LR-TDDFT/CVS result but it is important to consider the cost of either calculation. To do this, we first interrogate the simulation length (t max ) that is required to obtain the experimental feature. The TDKS spectrum shown in Fig is a well-converged result based on t max = 600 a.u. (≈ 14.5 fs) of simulation time, and in Fig we recompute this spectrum based on successively shorter simulations, down to t max = 75 a.u. (≈ 1.8 fs). Artifacts can certainly be observed in spectra obtained from shorter-time simulations, including negative intensities at some excitation energies, and the unfiltered spectra obtained at different values of t max differ significantly from one another. Upon dipole filtering, however, the two peaks that characterize the nitrogen near-edge can be observed even for the shortest simulation. In fact, these peaks shift only by ∼ 0.1 eV from t max = 75 a.u. to t max = 600 a.u.. Monitoring the filtered spectrum thus provides an incisive convergence metric whereas the the unfiltered spectrum does not.