Similarity in air and nitrogen I. Breakdown voltages

Measurements of the static breakdown voltage V_s of air and nitrogen have been made under uniform field conditions for values of N in the range 1·65×10¹⁹-9·9×10¹⁹ cm⁻³ and 0·33×10²⁰ less-than-or-eq, slant Nd_s less-than-or-eq, slant 2·64×10²⁰ cm⁻² (N is the gas number density and d_s the sparking distance.) The measurements show that Paschen's Law, V_s=f(Nd_s), is obeyed in nitrogen, but an interesting deviation is revealed in air. The observed deviations from Paschen's Law are in good agreement with the deviations which were calculated by Daniel et al. in 1969 from measurements of the spatial growth of pre-breakdown ionization currents.