Finally, in cases where the electride state possesses a band-gap, ultraviolet-visible (UV-Vis) or near-infrared (IR) spectroscopies could measure energies associated with transitions from the s → p states (assuming a Jortner-like model). We are looking forward to these experimental developments that provide further evidence of deviations from the TFD model, while at the same time giving experimental results against which first-principles techniques can be benchmarked.