The formation of high-mobility holes and satellite ions

The formation of high-mobility holes and satellite ions . As was briefly mentioned above, radiolysis of hydrocarbons results in the formation of several types of cationic species besides the solvent holes. Most of these satellite ions are generated within the first nanosecond after the radiolytic pulse. 

Transient absorption spectra of some satellite ions closely resemble the spectra of olefin radical cations. In cyclohexane, a band centered at 270 nm (at 2 ns [22]) is observed from 250 ps [25] after the ionization event (this band overlaps with the strong 240 nm band of cyclohexyl radicals [22]). The scavenging behavior and the decay kinetics of the UV-absorbing species suggest that they are normally-diffusing radical cations [25]. In the first few nanoseconds after the ionization event, the VIS absorbance is dominated by solvent excited states [22,57]. When the thermalized electrons are rapidly scavenged using a suitable electron acceptor (halocarbons or N2O), this 

In some cases, the identity of paramagnetic satellite ions was established by ODMR [42,44,48]. For example, 9,10-octalin + was identified in decalins and their solutions [42]. ODMR spectra of satellite ions in cyclohexane were related to EPR spectra of matrix-isolated cyclohexene + (Note that in the liquid cyclohexane, cyclohexene + undergoes a fast ring-puckering motion that averages hyperfine coupling constants for equatorial and axial protons, so the the EPR spectra of cyclohexene + in liquid and solid matrices are different) [42,44,48]. In both of these cases, the olefin radical cations were formed in spurs rather than in a reaction of the solvent hole with the olefin in the solvent bulk [42] (octalins gradually accumulate as radiolytic products). Olefin satellite ions were also observed in squalane [24]. 

How do these satellite ions form in the early stages of radiolysis Two ideas were put forward [1,37,42]. First, the satellite ions could be generated by fragmentation of short-lived electronically- and/or vibronically-excited solvent holes formed upon the ionization of the solvent, for example 

Reaction (3) is exothermic even for the ground-state alkane radical cations (0.4-0.6 eV) but requires overcoming a high potential barrier. Several authors (e.g., [22, 37]) have considered the possibility of deprotonation of the excited hole. 

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