On amplification of intensity of absorption spectra of fullerene C60 in long-wave region

The electron absorption spectra of fullerene C60 and its two dimers in the range of 200–800 nm have been studied. Calculation of the electronic and electron-vibrational spectra of fullerene in the region of 350–400 nm in the Frank–Condon approximation, as well as comparison with experimental spectra, shows that the spectra in the region of 200–400 nm correspond to the structure of only the fullerene C60 monomer, regardless of the concentration of the solution. In the region of 400–800 nm, the experimental absorption spectrum of fullerene C60 measured in $n$-hexane solution agrees well with the calculated electronic absorption spectrum of one of the fullerene dimers, which indicates the spontaneous formation of this dimer in concentrated solutions of fullerene C60. The intensity of the absorption bands of another dimer in this area increases significantly, which makes it possible to use the electronic spectra of fullerene C60 to solve practical problems, for example, in medicine.