Manuel Alonso1, José P. Santos2, Esther Hontañón 2, Emilio Ramiro2

  • 1 National Center for Metallurgical Research (CSIC), Avenida Gregorio del Amo, 8. 28040 Madrid, Spain
  • 2 RAMEM S.A., Sambara 33, 28027 Madrid, Spain

Received: November 30, 2009
Revised: November 30, 2009
Accepted: November 30, 2009
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Cite this article:
Alonso, M., Santos, J.P., Hontañón, E. and Ramiro, E. (2009). First Differential Mobility Analysis (DMA) Measurements of Air Ions Produced by Radioactive Source and Corona. Aerosol Air Qual. Res. 9: 453-457.



A recently developed Differential Mobility Analyzer (DMA) of high resolving power (50 for ions of mobility equivalent diameter ~1 nm) has been used to measure the mobility distribution of laboratory air ions generated by 241Am and corona discharge. In the case of 241Am, it has been possible to follow the changes in mobility during the early stages of ion aging: within the time interval between 10 and 30 ms after ion formation, the mean reduced mobility of positive ions decreased from 1.30 to 1.15 cm2/Vs, and that of negative ions from 2.0 to 1.75 cm2/Vs. The mobility distribution of air ions at the outlet of a corona ionizer strongly depends on the corona voltage, mainly due to the mobility-dependent extent of electrostatic losses within the ionizer. The mean reduced mobility of corona ions ranged between 1.01 and 1.20 cm2/Vs (positive) and 1.76 and 1.96 cm2/Vs (negative).

Keywords: Differential mobility analyzer; Corona discharge; Resolution; Ion aging; Radioactive source

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