Investigation of thermal electron attachment to organic acetates and aromatic halogen derivatives

A new thermal electron attachment mechanism is proposed. The importance of this mechanism is that the activation energy for dissociative thermal electron attachment is equal to the change in internal energy for the process. It is therefore possible to determine electron affinities for radicals and bond dissociation energies providing one of these quantities is known. The results of three compounds leading to the electron affinity of the acetate radical are presented. The electron affinity of the acetate radical determined by this technique compares favorably with the electron impact value. Thermal electron attachment studies to some aromatic halogen derivatives are also presented. In particular, the thermal electron attachment of 3'- and 4'- chloroacetophenone shows a unique temperature dependence involving three different phenomena. This adds further support to the thermal electron attachment mechanism proposed earlier for the aromatic halogen derivatives. The relationship between thermal electron attachment and electron beam studies of dissociative electron attachment to the aromatic halogen derivatives is also shown. An empirical negative ion potential energy function is used to show this relationship. Use of this potential energy function permits a more quantitative representation of the thermal electron attachment mechanisms previously proposed. In some cases, the mechanisms have been altered from the earlier qualitative interpretation. Although the modes of electron attachment are quite different, the two techniques of studying dissociative electron attachment appear to be essentially in complete agreement.