# Electrons below 0 kelvins

1. Mar 5, 2005

### floped perfect

If an atom was below zero Kelvins, or at zero Kelvins, would it be possible that the electrons would lose their energy level completely and the atom would collapse?

2. Mar 5, 2005

### kirovman

Below zero Kelvin? You are suggesting negative temperature.

That's not possible I'm afraid. You would have to take more thermal energy out of the atom than it had in it in the first place.

I read something about negative temperature in Quantum Statistics, but I think it was a model, not a reality.

3. Mar 5, 2005

### ZapperZ

Staff Emeritus
The solutions to the atomic energy level are solved, in principle, at T=0K. When we say this is the GROUND STATE state energy level, we mean it.

Zz.

4. Mar 7, 2005

### Astronuc

Staff Emeritus
There is a reason that we call T=0 K "Absolute Zero".

Temperature is a measure of "atomic" kinetic energy.

5. Mar 7, 2005

### dextercioby

It was a model describing reality... Yes,under certain conditions,you can obtain negative temperatures.

Daniel.

6. Mar 7, 2005

### marlon

Yes it can be....But then again that is very exotic. For example in some spin-systems (i mean many atoms and we only look at spin spin interactions) absolute NEGATIVE temperatures can arise. These temperatures are no really negative, but they need to be looked at as bigger then infinity....

The conditions for this to occur are for example that the spin-spin relaxation time is little compared to the spin lattice relaxation time. This means that the spins mutually interact long before thermal degrees of freedom come into play...

regards
marlon

7. Mar 7, 2005

### misogynisticfeminist

hey, this is really interesting. Is there a name for this phenomenon? Can i have more information or articles regarding this??? Thanks alot.......

8. Mar 7, 2005

### ohwilleke

To even think about a subzero kelvin temperature you pretty much have to define what kelvin temperature means. The customary definition of kelvin temperature is incapable of being below zero in any possible configuration of atoms with any possible momenta.

9. Mar 7, 2005

### marlon

http://boojum.hut.fi/research/magnetism/zero.html [Broken]

marlon

Last edited by a moderator: May 1, 2017
10. Mar 7, 2005

### ohwilleke

From the above link:

Last edited by a moderator: May 1, 2017
11. Mar 7, 2005

### humanino

true my dear Godfather
the right quantity to look is $$-\frac{1}{kT}$$ which remains continous in that case. Somehow, negative temperature are "higher" than positive temperature, and in reverse order (so the highest of all is near 0 and negative) if I remember correctly. In any case, it is a very simple exercise of statistical physics

12. Mar 7, 2005

### kirovman

Yes that's the one I saw in Quantum Statistics. Only touched on it briefly though, and I didn't bother learning it for the exam (luckily never turned up).
The lecturer was awful for teaching this material!

I'm quite interested now though, I will go back and read a bit more.

13. Mar 8, 2005

### Creator

True,... just depends on how you define temperature.

Before the development of the laser, population inversion was commonly referred to as a negative temperature based on standard thermodynamics.

Here's quote from an article:
"Simply adding energy by thermally agitating the medium is not sufficient (under thermodynamic equilibrium) to produce a population inversion, because heat only increases the average energy of the population, but does not increase the number of species in the excited state relative to that in the lower state. The ratio of the number of atoms at two energy levels (1 and 2) under thermodynamic equilibrium is given by the following equation:

N2/N1 = exp[- (E2 - E1) / kT]
where N(1) and N(2) are the number of atoms in level 1 and level 2, respectively, E(1) and E(2) are the energies of the two levels, k is the Boltzmann constant, and T is the temperature in kelvins. As demonstrated by the equation, at thermodynamic equilibrium, N(2) can be greater than N(1) only if the temperature is a negative number. Before the research describing maser and laser action was published, physicists referred to a population inversion as a negative temperature, which was symbolic of their view that any condition other than thermodynamic equilibrium was unlikely to be sustained....."