Ion mobilities and transport cross sections of daughter negative ions in N2O and N2O-N-2 mixtures

Abstract

A pulsed Townsend apparatus is used to measure the mobility of a single negative ion species in N2O and N2O-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 N2O2-. A reaction scheme involving ion conversion and electron detachment is presented, ending with the formation of a stable N2O2- ion. The momentum transfer integral cross section for N2O2- in pure N2O 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 N2O-N-2 mixture.