A study of alkyl radicals in the matrix of polycrystalline n-alkane irradiated at 77 K - 2. Effect of intra- and intermolecular interactions on radical formation in n-heptane polycrystals

To reveal the reasons for the previously found absence of end radicals upon gamma-radiolysis of n-heptane polycrystals, we performed quantum-chemical calculations (SCF-MO, RHF, 6-31G* basis set) of the n-heptane molecule and its four radicals. The energies of the crystal lattice were calculated by t he atom-atom potential method. Comparison of the experimental and calculate d data showed that the absence of the end radicals is not related to the in termolecular interaction in the crystals. The most probable reason for the selective radical formation upon radiolysis can be a transfer of the excita tion energy within the n-heptane molecule occurring before the radical form ation.