Detection of Electronic Coherence via Two-Dimensional Electronic Spectroscopy in Condensed Phase

Two dimensional Fourier transform electronic spectroscopy (2DES) in the visible region enables direct observation of complex dynamics of molecules including quantum coherence in the condensed phase.This review aims to provide a bridge between the principles and intuitive physical description of 2DES for tutorial purpose.Special emphasis is laid upon how 2DES circumvents the restrictions from both uncertainty principle and the wave-packet collapse during the coherent detection, leading to the successful detection of the coherence in terms of energy difference between the eigenstates showing as the quantum beats; then upon the possible mixing among the pure electronic transition, single-mode and multi-mode coupled vibronic transition leading to the observed beating phenomena.Finally, recent advances in experimentally distinguishing between the electronic coherence and the vibrational coherence are briefly discussed.