Abstract: Configurations of C50 fullerene and its two dimers C100 and C101 were optimized at B3LYP/6-31G* level. On the basis of the optimized geometrical structures, their excited states, electronic absorption spectra and third-order nonlinear optical polarizabilities in different optical processes were investigated at TDB3LYP/3-21G* level coupled with sum-over-states method. The results obtained from the electronic absorption spectra showed that the largest wavelength absorption peaks of C50 fullerene dimers had a remarkable red shift compared with that of C50 fullerene, and their third-order nonlinear optical polarizabilities increased after the dimerization. Especially, [5,5]-[5,5] dumbbell-like C50 fullerene dimer C101 had a larger third-order nonlinear optical polarizability than [2+2]-closed C50 fullerene dimer C100.

Key words: C50 fullerene, Dimer, Absorption spectrum, Third-order nonlinear optical polarizability