Effect of temperature on the mobility of ions

Abstract

The effect of temperature, between 87 and 250{degree}C, on the mobility of protonated amines in helium, air, CO{sub 2}, and SF{sub 6} was studied by ion mobility spectrometry. In helium, the reduced mobility was found to decrease as the temperature was raised, due to an increase in the collision cross section, and was approximately proportional to T{sup {minus}1/2}. In CO{sub 2}, where clustering takes place at low temperatures, raising the temperature led to an increase in the reduced mobility, mainly due to breakdown of the clusters and a decrease in the effective mass of the ion. In air, where only little clustering was observed, the reduced mobility of light ions increases with the temperature, while for heavy ions the opposite was found. In SF{sub 6}, like in CO{sub 2}, the increase of the reduced mobility with temperature was attributed to breakdown of clusters. An expression for the temperature dependence of the reduced mobility in each of these drift gases was determined semiempirically.