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

TL;DR

This study uses advanced quantum simulations to analyze ultrafast electronic and structural dynamics in coronene and circumcoronene, revealing that their structural behavior is similar despite spectral differences, supporting coronene as a model for larger PAHs and graphene nanoflakes.

Contribution

The paper demonstrates that coronene can serve as an effective model for studying ultrafast dynamics in larger PAHs and graphene nanoflakes through detailed non-adiabatic quantum simulations.

Findings

Structural dynamics are identical in coronene and circumcoronene.

Breathing and tilting motions govern decay dynamics.

Absorption spectrum differences are due to electronic delocalization.

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.