Total EPD spectrum of Ada⁺ in the spectral range 10,000–33,000 cm⁻¹ compared to stick spectra of vertical transitions of Ada⁺ originating from its ²A₁ ground electronic state obtained by TD-DFT calculations (B3LYP/aug-cc-pVTZ; Table 1). The gray dotted line, generated using a spline from the part of the curve between the peaks, is subtracted from the spectrum to analyze the vibronic peaks (labeled A–E) in Figure 4.