Neutron bombardment of C60 and C70 fullerenes: A spectroscopic and calorimetric study

C-60 and C-70 fullerenes were neutron-bombarded to an integral dose of 3.28x10(16) n cm(-2). After the neutron treatment the trichloromethane soluble fraction was determined spectrophotometrically and C-60 insoluble fraction was found at 3.8% while the insoluble fraction of C-70 17.9%. The formation of the CHCl3 insoluble fraction is due to polymerization and incipient amorphization of the neutron-bombarded fullerenes where C-70 appears more sensitive to radiation damage than C-60. Raman spectroscopy was used for the characterization of the irradiated fullerenes as well as electron spin resonance (ESR) and electronic absorption spectroscopy on solid samples. Differential scanning calorimetry (DSC) to 630 degrees C was employed for the determination of the Wigner energy of the neutron-damaged fullerenes. The results are consistent with a higher level of radiation damage reached by C-70 in comparison to C-60 at the same neutron dose.