Visualization of Photoinduced Charge Transfer and Electron–Hole Coherence in Two-Photon Absorption

We provide a visualization method to observe the photoinduced charge transfer and electron–hole coherence in the two-photon absorption (TPA), especially including the optical properties in the “hidden” intermediate states in TPA. A new method for analyzing the characteristics of two-photon excitation is proposed using a two-step process, which is closest to the physical reality process. These visualization methods include transition density matrix, charge density difference, and transition dipole moment in TPA involving both ground and excited state wavefunctions and the transition dipole moments among electric transitions from ground to intermediate and to final excited states. Our visualization method of photoinduced CT and electron–hole coherence in TPA can promote deeper understanding and design molecules with large cross sections in TPA.