Ultrafast Nonadiabatic Electron Relaxation Dynamics in Photoexcited C60 Molecules.

Fullerene molecules, being attractive for fundamental research and key building blocks in materials of energy harvesting, are important for ultrafast electron transfer studies. The nonradiative electron-relaxation dynamics in a C₆₀ molecule is investigated after chosen initial photoexcitations. The methodology includes nonadiabatic molecular simulation combined with time-dependent density functional theory and a semiclassical surface hopping approach. Results treating the exchange-correlation by using hybrid functionals, Becke three-parameter Lee-Yang-Parr (B3LYP) and Perdew-Burke-Ernzerhof (PBE0), are presented. Both approaches produce similar unoccupied band structures in the ground state that qualitatively agree with our many-electron excited state calculation. The model-dependent differences in the ultrafast population dynamics, including the transient entrapment of the population, are studied systematically. The trend of the results demonstrates a universal dependence on the structure of the unoccupied band offering a spectroscopic route to probe the structure. Predictions can be assessed by comparison with ultrafast transient absorption or time-resolved photoelectron spectroscopy measurements. By selectively comparing with inexpensive nonempirical PBE results, the study facilitates method optimization for future studies of technologically important and larger fullerene complexes.