Synthesis of Cl₂ induced by low energy (0-18 eV) electron impact to condensed 1,2-C₂F₄Cl₂ molecules

The interaction of low energy electrons (0-18 eV) with C₂F₄Cl₂ molecules condensed in multilayer amounts on a cryogenically cooled Au substrate generates Cl₂, as can be seen from the energy and temperature dependence of the Cl^- desorption signal. The cross section for Cl₂ formation exhibits two pronounced resonant features with maxima near 0 and 10 eV, dropping to essentially zero in the energy range between the resonances (near 3 eV). The energy dependence of the reaction cross section qualitatively follows that of Cl^- desorption, which itself can be correlated to dissociative electron attachment (DA) processes in the gas phase. While at 10 eV excited negative ion resonances and electronically excited states of neutral C₂F₄Cl₂ may be involved in the process, in the low energy region (<2 eV) the reaction can only be initiated by dissociative electron attachment. Possible reaction pathways are discussed.