Ionization coefficients in nitrogen

Primary and secondary Townsend ionization coefficients, α and ω/α, were determined for nitrogen over the range 100< E/p 0 <470 v cm −1 torr −1 from data on the spatial growth of currents in uniform fields. Values of α/ p 0 were found to be smaller than those previously published for mercury-contaminated gas, the difference being particularly noticeable at higher values of E/p 0 and correspondingly lower pressures. Theoretical calculations of α, based on the Maxwellian distribution for electron energies, gave values comparable with those measured experimentally at E/p 0 similar 120 v cm −1 torr −1 ; calculations at higher electron energies would require large extrapolations of electron drift velocities and temperatures. The observed variation of ω/α with E/p 0 can be explained quantitatively by assuming resonance neutralization of an ion to occur as it approaches the metal surface of the cathode; for sufficiently high approach velocities Auger de-excitation follows.