Attachment of slow (<1 eV) electrons to O2 in very high pressures of nitrogen, ethylene, and ethane

The results of a recent study on the capture of slow (<1 eV) electrons by O2 embedded in very high pressures of nitrogen (up to 27 500 torr), ethylene (up to 17 000 torr), and ethane (up to 17 500 torr) are presented and discussed. Large changes have been observed in both the magnitude and the energy dependence of the attachment rate (and cross section) with increasing density of these three media. At sufficiently low pressures (≲ 1500 torr for N2; ≲ 2500 torr for C2H4; ≲ 3500 torr for C2H6), low-energy electron attachment to O2 can be treated approximately as a three-body process. However, as the density of each medium increases, each affects the capture process differently, demonstrating the profound effect and importance of the environment on the electron attachment process. Electron capture mechanisms and reaction schemes consistent with the observed dependences of the attachment rates on the density of each medium are presented and discussed. The high-pressure data on O2 in C2H4 and N2 have been successfully related to ``liquid-state'' behavior. From the O2, C2H4 data an autoionization lifetime equal to ∼2 × 10−12 sec has been estimated for O2−*.