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 sect ions thus determined increased significantly as the temperature was lo wered from 300 to 80 K for all ions investigated, which were fullerene C-60(+), cationized PEG polymers, cationized crown ethers, and proton ated and sodiated oligo-glycines. The temperature dependence of the co llision cross sections was successfully modeled by employing simple at om-atom interaction potentials including a repulsive R(-12) term and t he attractive long-range R(-6) and R(-4) terms, R being the distance b etween the colliding particles. (C) 1997 American Society for Mass Spe ctrometry.