The role of low-energy electrons in the high-energy radiolysis of condensedCF3I

Abstract

The dynamics of electron-induced reactions in condensed trifluoroiodomethane (CF3I) were studied under ultrahigh vacuum conditions. SevenCF3I radiolysisproducts (C2F6, C2F5I,C2F3I,CF2I2,C2F4I2,CFI3 andC2F3I3) were identified using temperature-programmed desorptionexperiments conducted after irradiation with 4 eV electrons. AlthoughC2F6 formation at energies above 4 eV is ascribed to electron-induced electronic excitationfollowed by prompt dissociation of the C–I bond to form radicals that dimerize, the formation of the other six radiolysis products at low sub-ionizationincident electron energies is attributed to dissociative electron attachment (DEA) because of theobserved resonance peaks in the radiolysis product yields as functions of incident electron energy (∼2 to ∼ 7 eV). Allseven CF3I electron-induced reaction products were also identified following irradiation with 500 eVelectrons. While dissociative electron attachment and/or electron impact excitation may playan important role in the high-energy radiation-induced synthesis of the high-yield productC2F6, a dramaticenhancement of up to ∼ 2 × 104 in product yield per electron at 500 eV relative to that at 4 eV for some products suggests,however, that DEA is not the dominant mechanism for the high-energy radiation-inducedsynthesis of those products.