Ozone is what you get if you apply enough energy to a set of three
oxygen molecules (O2) to temporarily tear 'em apart, and end up with
them being put back together into a pair of ozone molecules (O3).
Although this is often done using a strong electrical field, the
resulting ozone molecules can each have a neutral electrical charge -
they are not ionized. It's also possible to convert O2 to O3 by means
of high-intensity ultraviolet light - commercial ozone generators
often use this approach.



The ozonator in my hot tub works that way, it has a small quartz fluorescent
tube. It's nice because it reduces the bromine consumption though the
replacement tubes are pricey.