DIFFERENTIAL MOBILITY ANALYSIS OF MOLECULAR-IONS AND NANOMETER PARTICLES

Differential mobility analyzers (DMAs) can classify a steady and narro wly monomobile stream of charged particles from a continuum spectrum o f electrical mobilities. This feature has been widely exploited in aer osol research involving particles larger than some 10 nm. But high los ses and low resolution due to Brownian diffusion have traditionally im paired DMA use for smaller particle sizes. These aerosol instruments h ave thus been poor competitors with time of flight drift tubes for mob ility-based analysis of molecular ions and clusters, Recently, however , these problems have been overcome. Specially designed and run DMAs c an now supply a pure and steady stream of molecular ions or clusters i n a gas by classification from a complex ion mixture. The potential of such devices for investigations involving ions and nanoparticles is i llustrated through various examples of recent work. (C) 1998 Elsevier Science B.V.