Effect of dissociation energy on plasma ions behavior

[Si14]

Hi,
Suppose there are two plasma cases, conditions are the same, except for the gases present:
a-Oxygen
b-Nitrogen

Since the dissociation energy of nitrogen is higher than oxygen, what could be concluded from it? Could it be more energetic nitrogen ions than oxygen ions (because initially they needed more energy to dissociate?) or something else? Or could it be concluded that the average discharge current in case b is higher than case a because of this?

Thanks.

 

[alxm]

I don't think you can say much. The dissociation energy only tells you how strongly one atom binds to another; which doesn't have any direct relationship to the ionization potential.

If you look at it in terms of electronic levels, then the binding/dissociation energy corresponds to the relative shift in the occupied levels when two atoms get close to each other, whereas the ionization potential is their absolute value.

 

[Si14]

Thanks. Ok, I also know that the 1st ionization energy of nitrogen is higher than oxygen.
http://environmentalchemistry.com/yogi/periodic/1stionization.html

So knowing this, can I argue what I said in my 1st post that since the ionization energy is higher for nitrogen, compared to oxygen, can one say that the energy of electrons and ions in the nitrogen plasma is higher than the oxygen plasma?
On the other hand, since plasma deals with the ionization energy, I assume, then what can be concluded from higher ionization energy level of nitrogen compared to oxygen?

 

[alxm]

So knowing this, can I argue what I said in my 1st post that since the ionization energy is higher for nitrogen, compared to oxygen, can one say that the energy of electrons and ions in the nitrogen plasma is higher than the oxygen plasma? On the other hand, since plasma deals with the ionization energy, I assume, then what can be concluded from higher ionization energy level of nitrogen compared to oxygen?

You can't say the energy of the electrons and ions in the plasma would be higher; what that means to me would be saying that their kinetic energy is higher, i.e. a higher temperature. The thermodynamics of phase changes works just as well for plasma as any other. Basically the ionization energy represents part of the http://en.wikipedia.org/wiki/Latent_heat" for the phase transition from gas to plasma. Let's assume all else is equal (heat capacities and such), and assume a higher ionization potential means a higher latent heat (it probably does in almost all cases, but properly there's there's entropy to take into account), also meaning a higher temperature is required to form a plasma.

If you then consider a given amount of nitrogen and the same amount of oxygen at some temperature, and add the same amount of energy (enough to create plasmas) to both, then the oxygen plasma will be hotter, because less energy was spent turning it into a plasma. A direct analogy to a more conventional phase change would be if you took a given amount of water and ether and vaporized them with the same amount of energy (where we again, for the sake of argument assume equal heat capacities). Ether has a much lower latent heat of vaporization compared to water (because its intermolecular bonds are much weaker), so more energy would be 'left over' for heating it, and the ether vapor would be hotter than the water vapor.