Electroscope's discharge by UV-C light

An electroscope is charged by rubbing a rubber balloon against some wool and bringing it closer to the plate. When the plate is touched with a finger and the balloon is near it, the negative charges escape from the leaf, so after the finger is removed, an excess of positive charges remain on it. Then the air is ionized by using a germicidal lamp which emits UV-C radiation at 254 nm producing a lot of Ozone in the process. Freed electrons in the air nearby quickly neutralize the charges on the leaf until an almost complete discharge of the electroscope happens. The phenomenon is quick and apparent at first then becomes much slower.