Low-energy electron attachment to C6H5X (X = Cl, Br and I)

Rate constants for the dissociative electron attachment to C6H5X (X = Cl, Br and I) have been measured in Xe buffer gas at room temperature in the mean electron energy region between 0.04 and /2~ 2 eV using the pulse-radiolysis microwave-cavity method combined with microwave heating. Cross sections as a function of electron energy have been derived by unfolding the obtained rate constants. The rate constants for C6H5I decrease with the mean electron energy, while those for C6H5Br and C6H5Cl exhibit drastic increases, by about two and four orders of magnitude, respectively. The cross sections for C6H5I show a maximum at /2~ 0 eV, and those for C6H5Br and C6H5Cl have a peak at 0.3 and 0.7 eV, respectively. These differences are brought about mainly through the difference in the dissociation energy of the C6H5-X bond.