Appearance Potential of CF3+ in the Dissociative Photoionization of CF3Br

Measurements of the appearance potential for the production of CF3+ in the photoionization of CF3Br are in sharp disagreement, contributing to controversy in the heat of formation of CF3+. We reexamine our previous work and add additional experiments, obtaining AP(CF3+/CF3Br) = 11.64 +/- 0.04 eV as the average of four measurements made under widely different conditions. This is higher by 0.08 eV than the value we reported previously. Our new value for Delta(f)H0 degrees (CF3+) is now 88.0 +/- 0.9 kcal mol(-1). We compare our method with other techniques.