Initial Elementary Processes In Tetrafluoroethylene Plasma - An Ab-Initio Molecular-Orbital Study

Initial elementary processes in tetrafluoroethylene plasma are studied by using an ab initio molecular orbital method. The energy-surfaces at excited states are obtained by the Hartree-Fock method with a double zeta basis set, plus Rydberg orbitals. A pi-pi* transition is low-lying both at singlet and triplet excited states. Vinyl-polymerization-type reactions are expected in the presence of some radical species via these transitions. The C=C bond cleaves via a triplet pi-sigma* transition to form CF2. The predicted elementary processes via there states are compatible with experimental results that C2F4* and CF2 are primary precursors. No excited states that bring about a C-F bond cleavage are obtained within 10 eV of the ground state. As a path for a C-F bond cleavage, a dissociative electron attachment process is found in a low energy region. This process is considered to be important for producing fluorine anions.