Coronene: a model for ultrafast dynamics in graphene nanoflakes and PAHs

Abstract

Assuming a delta pulse excitation, quantum wavepackets are propagated on the excited state manifold in the energy range from 3.4–5.0 eV for coronene and 2.4–3.5 eV for circumcoronene to study the time evolution of the states as well as their lifetimes. The full-dimensional (102 and 210 degrees of freedom for coronene and circumcoronene respectively) non-adiabatic dynamics simulated with the ML-MCTDH method on twelve coupled singlet electronic states show that the different absorption spectra are only due to electronic delocalisation effects that change the excited state energies, but the structural dynamics in both compounds are identical. Breathing and tilting motions drive the decay dynamics of the electronic states away from the Frank–Condon region independently of the size of the aromatic system. This promising result allows the use of coronene as a model system for the dynamics of larger polycyclic aromatic hydrocarbons (PAHs) and graphene one dimensional sheets or nanoflakes.