EFFECT OF CHARGING AND NEUTRALIZATION ON THE MOBILITY DISTRIBUTION OFNANOMETER-SIZED AEROSOL-PARTICLES

The charging and neutralization of aerosol particles by ions can take place through (1) ion attachment to the surface of aerosol particles, or else (2) electron transfer between the ions and the molecules of th e aerosol particle surface. To decide which of the two mechanisms is c orrect, a careful experimental investigation has been carried out usin g ultrafine aerosol particles having electrical mobilities of the same order of magnitude as those of the ions. If the ion attachment mechan ism were correct, one would expect a shift in the aerosol mobility dis tribution after several stages of charging and neutralization. Such a shift has not been detected in our experiments. This result supports t he electron transfer mechanism as the correct one, and demonstrates th at the size of ions have no effect on the size distribution of particl es measured by a differential mobility analyzer, even in the extreme c ases in which the sizes of ions and particles are of the same order of magnitude. Copyright (C) 1996 Elsevier Science Ltd.