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 Cl-2, as can be seen from the energy and temperature dependence of the Cl- desorption signal. The cross section for Cl-2 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.