Significance of Loosely-Bound Electrons

Anions that are formally unbound but metastable can be chemically important. These temporary anion resonances are discussed in detail later 

In view of this, it has been proposed that hydrated electrons generated on the surface of stratospheric ice crystals, via cosmic rays, could contribute to Cl formation via DEA of adsorbed CFCs. Photodetachment of the chloride ions might then provide a mechanism to generate the Cl radicals that lead to ozone destruction. However, attempts to link these laboratory observations directly to stratospheric ozone chemistry have been strongly criticized, although modeling does leave open the possibility that, at the very least, HCl destruction on ice crystals might be important for stratospheric chlorine chemistry. More work is evidently needed to resolve this controversy. 

Assuming that the products R + R are lower in energy than the reactants (Rj - R2 plus an infinitely separated electron), then the intermediate species (Rj - R2) is a temporary anion resonance, since the bound-state configuration of moieties Rj, R2, and an extra electron is R -l-R, not the anion (Rj -R2) . Whether reaction [1] will occur in practice depends sensitively on the barrier(s) and nonadiabatic couplings involved in the second step (nonadiabatic transition to the dissociative a state), as well as the energy of the incident electron, which controls whether the temporary anion resonance can be accessed or not. 

Moving from the gas phase into solution, there is evidence that very low-energy electrons can damage via a DEA mechanism some- 

In addition, for a weakly-bound anion it may be necessary to consider the possibility that the molecule s vibrational motion could access regions of the potential energy surface where the anion is no longer thermodynamically stable with respect to electron ejection (autodetachment). For weakly-bound anions in the gas phase, autodetachment induced by rotational motion may also need to be considered.  

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