The reaction HCl~+ + CF_4- HCF_4~+ + Cl: Implications for the heat of formation of CF_3~+

摘要

For some years there has been a dispute concerning the appearance energy of CF_3~+ from CF_4 [AE(CF_3~+/CF_4)], or alternatively, the ionization energy of CF_3[IE(CF_3)] or the heat of formation of CF_3~+[DELTA_fH(CF_3~+)]. In an earlier work [M. Tichy, G. Javahery, N. D. Twiddy, and E. E. Ferguson, Int. J. Mass Spectrom. Ion processes 79, 231 (1987)] the reaction between HCl~+ was used to support a low value, AE(CF_3~+/CF_4)=14.2eV. A remeasurement of this reaction over the temperature range 173-500 K shows that the original study was in error, both in the reported rate constant and the ion product. In the present work, the rate constant was found to be collisional, producing HCF_4~+. The rate constant for thermal decomposition of HCF_4~+ into HF+CF_3~+ was measured in the course of this work. These new measurements bring into harmony AE(CF_3~+/CF_4) obtained from the HCl~+ reaction and the value AE(CF_3~+/CF_4)=14.67(+-)0.04 eV reported by R. L. Asher and B. Ruscic [J. Chem Phys. 106, 210 (1997)].