Effect of the long-range potential on ion mobility measurements

The temperature dependence of ion mobilities in helium was studied by using the ion chromatography method to investigate the effect of long-range terms in the ion-buffer gas interaction. Experimental cross sections thus determined increased significantly as the temperature was lowered from 300 to 80 K for all ions investigated, which were fullerene C-60(+), cationized PEG polymers, cationized crown ethers, and protonated and sodiated oligo-glycines. The temperature dependence of the collision cross sections was successfully modeled by employing simple atom-atom interaction potentials including a repulsive R(-12) term and the attractive long-range R(-6) and R(-4) terms, R being the distance between the colliding particles. (C) 1997 American Society for Mass Spectrometry.