Dissociative Electron Capture in Water Vapor

An electron swarm experiment has been conducted to study the process of negative-ion formation in water vapor by dissociative electron capture. Assuming that electrons are captured in a single process at one well-defined energy, the present results are consistent with a beam experiment reported by Buchel'nikova. It was found that the capture cross section, (due to the formation of H^-), when integrated over energy, was 7.7×{}10^-18 cm² ev, which is consistent with the electron beam results of 6.5×{}10^-18 cm² ev. The energy at which the process peaks was found to be 6.4 ev, which agrees quite well with the peak energy found by Buchel'nikova, but in general disagrees with other values obtained by mass spectroscopy.