Enhanced thermal dissociation of optically excited C-60 chains

The thermal dissociation of C-60 polymers has been studied using Raman scat tering. The measured dissociation rate depends on the intensity of the 1064 nm NIR excitation, showing that i) the band gap is smaller than 1.17 eV an d) a radiation-enhanced thermal breakdown path exists in addition to the "n ormal" thermal breakdown mechanism. Quantum chemical calculations show that the energy barrier E-a for thermal breakdown is about 40% lower in the fir st (optically) excited state than in the ground state. This agrees well wit h the ratio between our radiation-enhanced value E-a = (1.1 +/- 0.02) eV an d values near 1.9 eV measured by purely thermal methods.