Debye Layer

Clausius2

Just a question:

I do know it is possible to have a debye layer in a electrolyte. But is it posible to have a Debye layer in air?. I mean, if I put a single charged particle in air, do I have a layer of ionized air surrounding it??.

Thanks.

Gokul43201

You are talking about debye screening, right? If my memory serves me, the debye screening model assumes the presence of "free" charges in the system - that is an initial condition of the sytem, if I may call it that.

In a neutral gas like air, you have no free charge. What you do have, however, are polarizable molecules (though O2 and N2 have pretty low polarizabilities). This gives rise to dipolar (or dielectric) screening which, unlike debye screening doesn't not really change the functional form of the potential very much (ie: a 1/r potential remains roughly a 1/r potential) . Nevertheless, the charge-dipole interaction is likely to be too weak (compared to KE) at most temperatures to create anything like a debye layer.

Also, I can't imagine there is enough of a field gradient from an isolated charge to ionize nearby molecules.

However, if you put a charged particle in pure water, you would have a layer of polarized (not ionized) water molecules surrounding it (and resulting in debye-like screening of the charge potential). This is essentially what hydration/dissolution involves.

Clausius2

Thanks gokul, I got it. Air is not an electrolyte at all.