The initial conditions were sampled from the harmonic quantum Boltzmann distribution at 298 K using the normal modes analysis of TS. In addition, the TS state of the Diels-Alder reaction of C60 with 2,3-dimethyl-1,3-butadiene has several low-frequency modes which can result in very distorted structures in normal mode sampling (as observed before for similar sampling procedures 44 ), hence, we set these frequencies as 100 cm -1 if they are smaller than this value; this procedure was introduced here but later found useful also in the context of nonadiabatic dynamics submitted earlier than this work .