Re: [Phys-l] Negative kelvin temperatures

["Krishna Chowdary" <professor.head@gmail.com>]

On 2/6/07, Dan Crowe <Dan.Crowe@loudoun.k12.va.us> wrote:
> On another list, the claim was made that in a system with a finite
> number of energy levels, population inversion implies a negative kelvin
> temperature.  The following Wikipedia article was cited as evidence:
>
> http://en.wikipedia.org/wiki/Negative_temperature
>
> I had never heard this claim of negative kelvin temperature before.  My
> first reaction is that a system with population inversion is not in
> thermal equilibrium, so it doesn't make sense to determine the
> temperature of a system based on population inversion.  I'm not even
> sure that the system has a well defined temperature.  Can someone
> familiar with this concept please discuss its merits?



I can't speak to the Wikipedia reference.

I perceive two questions here:

1)  Is there such a thing as negative temperature?

2)  Is negative temperature connected with a population inversion?

The first question is answered nicely in

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/neg_temperature.html

and

http://www.av8n.com/physics/neg-temp.htm

The second question is addressed in part 2 (Polarization and Energy) of the
second reference.  Of course, www.av8n.com is the site of frequent Phys-L
poster John Denker.


--
regards
-Krishna