LOW-ENERGY-ELECTRON ATTACHMENT TO C6F5X (X=F, CL, BR AND I)

Rate constants have been measured for electron attachment to C6F5X (X = F, Cl, Br and I) in Xe buffer gas at room temperature at the mean el ectron energy between 0.04 and 2 eV using the pulse-radiolysis microwa ve-cavity method combined with microwave heating. The cross sections a s a function of electron energy have been derived by unfolding the obt ained rate constants. The rate constants at thermal energy are all the same, around 2 x 10(-7) cm3 molecule-1 s-1, for C6F5X, and decrease m onotonically with increasing mean energy. The cross sections have a pe ak at almost-equal-to 0 eV for each compound. Only C6F6 shows another cross-section maximum at almost-equal-to 0.75 eV. The discrepancy in t he rate constants at thermal energy with those in previous reports is discussed.