Atmospheric ion mobility spectra near the ground

Abstract

The mobility spectra of positive and negative ions artificially produced in the ambient air near the ground were measured by using a newly constructed mobility spectrometer having parallel plate electrodes. The negative mobility spectra obtained by this spectrometer have a very sharp peak at 1.80 cm 2 volt −1 s −1, and the average negative ion mobility is estimated to be 2.40 cm 2 volt −1 s −1. In the positive ion mobility spectra, on the other hand, a rather broad peak is seen at 1.25 cm 2 volt −1 s −1. The average positive ion mobility is estimated to be 1.69 cm 2 volt −1 s −1. By comparing the result with recent mass spectrometric measurements and a model calculation, detailed discussions are given. Additional experiments were made to test for changes of the mobility spectra by using nitric acid and ammonia vapours, and gases in tobacco smoke.