RELAXATION PROCESS OF THE SELF-TRAPPING EXCITON IN C-60

When C-60 is photoexcited, a self-trapping exciton (STE) is formed: Th e bond structure is distorted from symmetry I-h to D-5d while the stat es A(1u) and A(2u) are pulled into the energy gap from highest occupie d molecular orbital and lowest unoccupied molecular orbital, respectiv ely. A dynamical scheme is employed to simulate the relaxation process of STE. The evolution of both bond structure and electronic states sh ows that the relaxation time to form STE is about 100 fs. It should be noted that this relaxation time is much shorter than that of charge t ransfer in C-60. The origin for this large difference is discussed.