Ion mobilities and transport cross sections of daughter negative ions in N 2 O and N 2 O–N 2 mixtures

A pulsed Townsend apparatus is used to measure the mobility of a single negative ion species in N 2 O and N 2 O–N 2 gas mixtures. The range of the density-normalized electric field, E / N , is 6.5–100 Td (1 Townsend = 10 −17 V cm 2 ) over the pressure range 10–250 Torr and temperature range 295–300 K. Based on previous work it is shown that the most likely drifting ion is . A reaction scheme involving ion conversion and electron detachment is presented, ending with the formation of a stable ion. The momentum transfer integral cross section for in pure N 2 O and N 2 gases is derived from the above measurements. The unfolded cross sections are used as an initial guess and then further improved by ensuring good agreement between Monte Carlo calculated mobilities and the experimental results for the N 2 O–N 2 mixture.