Long-lived oscillations in 2D spectra of chlorophylls are at the heart of an ongoing debate. Their physical origin is either a multi-pigment effect, such as excitonic coherence, or primarily stems from localized vibrations. In the present work, we analyze distinguishing characteristics of relative phase difference measured between diagonal- and cross-peak oscillations. While direct discrimination between the two scenarios is obscured when peaks overlap, their sensitivity to temperature provides a stronger argument. We show that vibrational (vibronic) oscillations change relative phase with temperature, while electronic oscillations are only weakly dependent. This highlights that studies of relative phase difference as a function of temperature provide a clear and easily accessible method to distinguish between vibrational and electronic coherences.
@article{arxiv.1311.3068,
title = {Distinguishing electronic and vibronic coherence in 2D spectra by their temperature dependence},
author = {Václav Perlík and Craig Lincoln and František Šanda and Jürgen Hauer},
journal= {arXiv preprint arXiv:1311.3068},
year = {2017}
}