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

Abstract

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.

Coupling between Harmonic Vibrations Influences Quantum Beating Signatures in Two-Dimensional Electronic Spectra

“…Taking recent studies of multicomponent vibrational wavepackets ,,,, in conjunction with the agreements that we observe between the multiple-DHO simulations and experimental TDI data, we posit that the single-DHO approximation breaks down more often than is commonly anticipated. Indeed, examination of the quantum beatmaps obtained in our previous study of perylenediimide-based monomers and dimers reveals that signatures of coupled vibrational and/or vibronic wavepackets are evident .…”

Electronic State-Resolved Multimode-Coupled Vibrational Wavepackets in Oxazine 720 by Two-Dimensional Electronic Spectroscopy

“…Two-dimensional electronic spectroscopy (2DES) is well suited to directly address the coupling between electronic states and to discriminate various coherences, such as electronic, vibrational, and vibronic coherence. , Recently, the investigations of the coupling among different vibrational modes through 2DES have been reported. , By comparison with the prediction of Franck–Condon analysis determined from density function theory (DFT) calculations, Dean et al have assigned several low-frequency modes on the 2D oscillation maps of methylene blue via 2DES to vibrational fundamentals, overtones, and combination coherences on the ground electronic state but without any excited-state coherence being observed . Our group has recently proposed a multivibrational mode-coupled displaced oscillator model based on the analysis of Feynman diagram to understand vibrational coherence of bacteriochlorophyll a (Bchl a) observed in 2D maps. − However, the congested signals presented in these works make the assignment of couplings among the excited vibrational modes difficult. More robust methods are still required to distinguish the contribution of vibrational coupling in 2DES.…”