Some Remarks on the Fragmentation of Excited Ions in the Radiolysis of Hydrocarbons

The fragmentation of excited ions in the liquid-phase radiolysis of hydrocarbons is explained by a new mechanism, which involves the fragmentation of a highly excited ion (M+**). The M+** ion is considered here to be the electronic excited states and to decompose by the following mechanism. The electronic excitation energy can spread over all C–C bonds in a molecule before its fragmentation and, when the mean excitation energy per C–C bond exceeds its bond energy, the excited ion decomposes instantaneously in one vibration. Further, the mass spectra of isobutane and isooctane are calculated by a simplified quasi-equilibrium theory by introducing the highly excited ion and are compared with experimental mass spectra and with the calculated values without introducing the highly excited ion.