AN APPROXIMATION OF THE BIPOLAR CHARGE-DISTRIBUTION FOR PARTICLES IN THE SUB-MICRON SIZE RANGE

In recent years there has been an increased number of investigations to determine particle size distributions for the submicron regime. These distributions are frequently obtained using a differential mobility analyser (DMA). Ray data from the DMA can be converted into a size distribution if the bipolar charge distribution for the aerosol is known. Hence the size distribution will be representative only if the bipolar charge distribution is accurately described. An analytical solution is obtainable for the Gunn theory, while the Fuchs model must be solved numerically. To permit a rapid calculation of the bipolar charge distribution in the size range 1-1000 nm, an empirical expression is presented to approximate the distribution calculated from the Fuchs model. 7 Refs.