Investigation of radiation resistance of fullerenes under irradiation with fast neutrons

Fullerenes C$_{60}$ and C$_{70}$ synthesized by the electric arc method and fractionated (purity grades of 99.99 and 99.90 wt%, respectively) were irradiated in a solid phase in the WWR-M reactor (Konstantinov Petersburg Nuclear Physics Institute, National Research Centre “Kurchatov Institute”, Gatchina, Russia) with the aim of determining the survivability in the range of fast neutron fluences $\Phi$ = 4 $\times$ 10$^{15}$–3 $\cdot$ 10$^{17}$ n/cm$^2$. The irradiated samples were dissolved in carbon disulfide, and intact fullerenes were extracted. With an increase in the fluence, their weight fraction in the samples $S(\Phi)$, a measure of radiation resistance of molecules, decreased, to a first approximation, exponentially: $S(\Phi) = \exp(-\Phi/\Phi_D)$. The estimated characteristic fluences were $\Phi_D$ = 2.4 $\times$ 10$^{17}$ and 4.0 $\times$ 10$^{17}$ n/cm$^2$ for C$_{60}$ and C$_{70}$, respectively.