|MadSci Network: Physics|
Well, if all you have to go on are the ionized particles, there's not much you can do to figure out just how they became ionized... An ion is an ion, once it's produced there's no way to tell if it happened by electron impact, photoionization, etc... Now, you could use a mass spectrometer to identify exactly which components of the air have been ionized... In this case you'd turn off the built in ionizer of the mass spectrometer and just let it sample ions from your mystery ionization source. Compare the mass peaks you find to the composition of air, and see if anything is NOT being ionized by your source... Maybe that would give you some sort of clue.
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