MadSci Network: Chemistry

Re: Oxygen ionizatin

Date: Sun Aug 2 17:06:31 1998
Posted By: John Christie, Faculty, School of Chemistry, La Trobe University, Bundoora, Victoria, Australia
Area of science: Chemistry
ID: 901874732.Ch

I will deal with your questions one at a time.

1) Oxygen ionizes in the presence of an energy discharge such as a 
UltraViolet lamp. Do the ionized oxygen atoms remain ionized as long 
as they are in the presence of the energy field? 

Once the oxygen atoms are ionized, they enter into a series of very rapid 
reactions, including recombinations with electrons to become neutral 
species again. They do not "remain ionized" much at all. But there is a 
continuing pool of ionized oxygen atoms because new ones are being formed 
all the time.

A side issue: you cannot form oxygen ions with a UV lamp. The quartz 
windows of the lamp will only transmit light of wavelength 160 nm or more; 
oxygen will only ionize efficiently in UV light of wavelength 130 nm or 
less. The oxygen reaction that you can drive with a UV lamp involves 
neutral atomic oxygen, which can be generated by photodissociation with 
light of 210 nm or less. The easier and more usual way to generate oxygen 
ions is in an electrical discharge.

2) How soon after being ionized do the oxygen atoms reform into Ozone?

Much less than one second. But the reaction that forms ozone does not 
involve oxygen ions; ozone is formed by

O + O2 + inert third molecule ---> O3 + third molecule

Atomic oxygen (O) is readily formed from oxygen ions; molecular oxygen (O2) 
is abundantly present in air anyway.

3) If an ionized oxygen atom has a -2 charge, how can these atoms 
bond into Ozone when they should be magnetically repulsed by one 

Ionized oxygen, as formed in an electrical discharge or by very low 
wavelength UV light has a +1 charge. The most readily formed ion is 
molecular oxygen missing one electron: O2+ . Atomic oxygen missing one 
electron, O+ , also enters into the reaction system, but it is a much 
higher energy species. Because of the electrostatic repulsion (not 
magnetic) between ions with like charge, the chemical reactions in the 
system do not involve two ions reacting together; it is always one ion with 
a neutral species.

4) Is there some way to speed up the decomposition of Ozone? 

There are many ways to speed up the decomposition of ozone. Ozone (O3) is a 
high energy form of oxygen, so it is quite ready to revert to the lower 
energy, more stable form of molecular oxygen (O2). There are many ways of 
achieving the transformation. Atomic chlorine or bromine -- from molecular 
chlorine or bromine and visible light -- are particularly effective as gas 
phase catalysts, as is nitric oxide. Nearly all organic substances are 
directly oxidized by ozone. Rubber perishes very rapidly into a powdery 
heap, for example. Reducing solutions -- ferrous sulfate or potassium 
iodide -- will effectively remove ozone from a gas bubbled through them.

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