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Electron Attachment and Detachment. I. Pure O2 at Low Energy

1966; American Institute of Physics; Volume: 44; Issue: 5 Linguagem: Inglês

10.1063/1.1726956

1520-9032

J. L. Pack, A. V. Phelps,

Atomic and Subatomic Physics Research

Electron attachment and detachment coefficients are reported for pure oxygen from analyses of the current waveforms observed in drift-tube experiments. The results are consistent with the identification of the negative ion as O2− with an electron affinity of 0.43±0.02 eV. The two-body collisional detachment coefficient for O2− in thermal equilibrium with the gas increases from 9×10−17 cm3/sec at 375°K to 1.4×10−14 cm3/sec at 575°K. The three-body attachment coefficient for thermal electrons increases from 2.0±0.2×10−30 cm6/sec at 300°K to 2.8±0.5×10−30 cm6/sec at 530°K. The O2− ions are found to survive at least 3×108 elastic collisions without de-excitation and so are believed to be in their lowest vibrational state. At low oxygen densities the current of detached electrons is separated from the negative-ion current by applying a high-frequency voltage to the control grid. At high oxygen densities the electrons and negative ions cross the tube in a narrow pulse at a drift velocity determined by the equilibrium concentrations of electrons and ions.