Chemical behavior of 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene,and related compounds as a key to understanding the specifics of radiation-chemical processes: 5. Energy-controlled positive-charge transfer processes

The initial radiation-chemical yields of consumption of hydrocarbons G₀(-RH), where RH is 5-vinyl-2-norbornene, 2-ethylidene-2-norbornene, or 2-vinylnorbornane, dissolved in the solvents (L) cyclohexane, carbon tetrachloride, tert-butylamine, and benzene during irradiation of their solutions at 40°C with ⁶⁰Co γ-rays were determined. The G₀(-RH) values were found to be linearly related to the first vertical ionization potentials (PI₁) measured for RH and L in the gas phase by means of photoelectron spectroscopy. It was shown that the RH consumption processes are controlled by species with the highest and lowest PI₁ values. It was concluded that these species are superexcited solvent molecules L** (PI₁ = 15.6–17.8 eV for cyclohexane) and isomeric (distonic) forms of the RH⁺ radical cations, not the parent L and RH molecules, respectively. In the case of RH = VNB, the radical cation in this form contains two allyl systems, of which one is cationic and the other (characterized by PI₁ = 7.1 eV) is radical.