Fig. 5

Sixth-order 2Q–0Q–1Q three-dimensional (3D) spectrum (real part) of TIPS–TAP²⁻ in THF. The 3D spectra shown are obtained by the sum of the rephasing and nonrephasing 2Q–0Q–1Q contributions. a Experimental and b simulated 3D spectra. Isosurfaces are drawn at −12, −10, −7, 7, 11, and 35% of the normalized signal amplitude. Contour lines are drawn at 0.1 steps as indicated by the color bar. The bottom projections of the solids show the purely absorptive 2Q–1Q 2D spectrum at T = 0 fs. The dashed lines in the ∆ℏω_T = 0 plane denote the energies of the main absorption band at 2.06 eV and the progression band at 2.23 eV along ℏω_t and the energies of the 2Q levels at 4.10 and 4.27 eV along ℏω_τ. The letters A, B, C, D mark peaks, which are discussed in the article