| Experiment | ( t_1 ) | ( t_2 ) | ( t_3 ) | Signal direction | |------------|----------|----------|----------|------------------| | Pump–probe | 0 | Variable | 0 | Collinear with probe | | Photon echo | Variable | 0 | = ( t_1 ) | ( k_s = -k_1 + k_2 + k_3 ) | | 2D spectroscopy | Variable | Variable | Variable (FT) | Phase-matched |
: Translating abstract math into visual paths that show how light pulses interact with matter. Density Matrix Basics : Introducing the Density Matrix ( | Experiment | ( t_1 ) | (