Figure 5.

FFT-amplitude maps of the oscillatory components at 160 cm^–1 (top) and 476 cm^–1 (bottom). The 2D map is shown in comparison as gray contour lines with full lines (dashed lines) for positive (negative) signals (see Figure 2 for comparison). The inset in the upper panel shows an energy ladder diagram explaining the peaks at ω₃ ≈ 16470 cm^–1. Electronic (vibrational) levels are depicted as horizontal full (dotted) lines. Bra-side and ket-side interactions and the resulting signal are shown as dashed, full, and wavy arrows, respectively. Absorption and excitation spectrum are shown in the lower panel for comparison.