M. Adachi et al., EXPERIMENTAL EVALUATION OF ION-INDUCED NUCLEATION IN NANOMETER-AEROSOL FORMATION BY ALPHA-RAY RADIOLYSIS OF SO2 H2O/N-2 MIXTURES/, Colloids and surfaces. A, Physicochemical and engineering aspects, 109, 1996, pp. 39-48
A new system for experimental investigation of ion-induced nucleation
in particle formation by alpha-ray radiolysis is developed. Particles
formed by ion-induced nucleation are charged bipolarly, but particles
formed by processes such as binary nucleation are electrically neutral
. A new irradiation chamber was developed that uses a low electric fie
ld to prevent particle neutralization and preserve the charge distribu
tion that results from alpha-ray radiolysis. The effects of the electr
ic held on particle charging and radical generation were evaluated the
oretically. From this analysis, it was determined that the optimum con
ditions for causing particle formation and preserving the charge distr
ibution can be achieved by using a 0.92 MBq(241)Am source and an elect
ric field of 2 kV m(-1) in the ionization chamber. Under these conditi
ons, the charge distributions of particles formed by alpha-ray radioly
sis in SO2/H2O/N-2 mixtures were measured for various SO2 and H2O conc
entrations. The charged-particle fraction decreased with increasing SO
2 concentration and was nearly independent of the H2O concentration. I
t was determined from the results that SO2 mainly activated binary nuc
leation through SO2-OH radical reactions that produced H2SO4 and forme
d neutral particles. In contrast, H2O activated both ion-induced and b
inary nucleation because both water ion clusters and OH radical were p
roduced from H2O molecules.