Electron-Ion Recombination in Air at EMP Fields

The electron-ion recombination coefficient in dry and moist air at atmospheric pressure was measured using a parallel-plate ion chamber and a pulsed electron beam. In moist air a value consistent with that expected from a process in which H20 acts as a third body was found at low field. At a field of 1000 V/cm (105 V/m), however, the value has fallen to that of the clustered, two-body rate, showing that three-body recombination is not a significant electron removal process at EMP fields. The equilibrium field was measured and found to be consistent with the value expected from the measured recombination coefficient.