J. Phys. Chem. A 2005, 109, 1541-1547
1541
Appearance Potential of CF3+ in the Dissociative Photoionization of CF3Br E. A. Walters* and J. T. Clay Department of Chemistry, UniVersity of New Mexico, Albuquerque, New Mexico 87131
J. R. Grover*,† Department of Chemistry, BrookhaVen National Laboratory, Upton, New York 11973 ReceiVed: September 13, 2004; In Final Form: December 3, 2004
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 ∆fH0°(CF3+) is now 88.0 ( 0.9 kcal mol-1. We compare our method with other techniques.
Introduction Reported measurements of the heats of formation of CF3 and CF3+ show interesting disagreement, with the range from smallest to largest being ∼0.5 eV. This problem has been documented and discussed by many workers.1-8 The discrepancy stems in part from measurements of the appearance potential for CF3+ from CF3Br. Noutary9 and Creasey et al.10 report 11.84 eV and 11.92 ( 0.02 eV, respectively. Jarvis and Tuckett and Jarvis et al.1,2 conclude that the probable value of IP(CF3) is
