Rate Coefficients for Dissociative Electron Attachment by Halomethane Compounds between 300 and 800 K

The temperature dependence of the rate coefficients for thermal energy dissociative electron attachment reactions has been measured for nine halomethane compounds. Rate coefficients for CCl 4, CFCl 3, CF 2 Cl 2, CF 3 Cl, CHCl 3, CH 2 Cl 2, CHFCl 2, CH 3 I, and CH 2 Br 2 were determined between 300 and 800 K from relative rate measurements by using SF 6 as a reference compound. A flowing afterglow−electron cyclotron resonance technique was employed. Mass spectral analysis of product negative ions confirmed a dissociative attachment mechanism. Semiempirical quantum mechanical calculations of the geometry change associated with negative ion formation were carried out.