Electron Attachment to POCl3: Measurement and Theoretical Analysis of Rate Constants and Branching Ratios as a Function of Gas Pressure and Temperature, Electron Temperature, and Electron Energy
AIR FORCE RESEARCH LAB HANSCOM AFB MA
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Two experimental techniques, electron swarm and electron beam, have been applied to the problem of electron attachment to POCl3, with results indicating a competition between dissociation of the resonant POCl3 state and collisional stabilization of the parent anion. In the electron beam experiment at zero electron energy, the fragment ion POCl2- is the dominant ion product of attachment 96 under single-collision conditions. Small amounts 2 each of POCl3- and Cl were observed. POCl3- and POCl2 were observed only at zero electron energy, but higher-energy resonances were recorded for POCl, Cl-, and Cl2- ion products. In the electron swarm experiment, which was carried out in 0.4-7 Torr of He buffer gas, the parent anion branching ratio increased significantly with pressure and decreased with temperature. The electron attachment rate constant at 297 K was measured to be 2.5 plus or minus 0.6 X 10exp -7cu cm sexp -1, with ion products POCl2 71 and POCl3 29 in 1 Torr of He gas. The rate constant decreased as the electron temperature was increased above 1500 K. Theory is developed for a the unimolecular dissociation of the nascent POCl3- and b a stepladder collisional stabilization mechanism using the average energy transferred per collision as a parameter. These ideas were then used to model the experimental data, which showed that Dexp o0Cl-POCl2- and EAPOCl3 must be the same within plus or minus 0.03eV.
- Physical Chemistry
- Theoretical Mathematics
- Particle Accelerators
- Nuclear Physics and Elementary Particle Physics