Okay Geezer. Nice question, 'what happens to an atom at 0K'.

The easy answer is that we can't reach that temperature. but the relevance is still there. What happens to it? And I like mine too :) How does it decompose if it never 'radiates' by itself?

Bohr's model of an atom is not the one used by QM it seems? It have instead been replaced by a 'probability model' based on Louis de Broglie question about if light could behave like both waves and particles, why shouldn't particles also behave like waves?

"Thus, electrons in an atom were not moving in orbits but filled an orbit as standing waves. Familiar electromagnetic radiation, like light, exists as traveling waves, moving through space at the velocity of light. A standing wave does not move, but vibrates between fixed points, like the string on a violin."

While Bohr's model of the atom could account for spectral lines, it still could not account for why electrons had quantacized angular momentum in atoms and why electrons could be in orbit in atoms, which would involve acceleration around the nucleus, without radiating away all their energy, which accelerated electrical charges do. The atom could simply not be a little solar system, based on charge rather than gravity, since electrons, on classical principles, would lose energy and fall into the nucleus.

Familiar electromagnetic radiation, like light, exists as traveling waves, moving through space at the velocity of light. A standing wave does not move, but vibrates between fixed points, like the string on a violin. The sine wave at right represents a whole wavelength. It has a portion with a positive magnitude, a portion with a negative magnitude, and a node, which has zero magnitude.

The ends of the wave, which also have zero magnitude, are usually not considered to be nodes. Half a wavelength would have no nodes; one and a half wavelengths, two nodes; and two whole wavelengths, three nodes. A one dimensional wave has nodes that are points, and it vibrates into two dimensions. Similarly, a two dimensional wave, like a wave of water on the ocean, has nodes that are lines, and it vibrates into three dimensions.

A three dimensional wave, which is what electrons in an atom would be, has nodes that are surfaces. Such surfaces can be planes, cones, or spheres. By analogy, we might want to say that a three dimensional wave would vibrate into four dimensions, but this aspect of the matter does not seem have been much discussed or explored. In electron waves, each non-spherical node represents a quantum of angular momentum.

Thus, a half wavelength, with no non-spherical nodes, is 0 angular momentum; a full wavelength, with one non-spherical node, is angular momentum; a wavelength and a half, with two non-spherical nodes, is 2 angular momentum; etc. "

But it still doesn't answer the question about an atoms dissipation of energy if left alone?

From the Quantacized Atom

Now take a look here

conservation_of_energy What we read here is firstly 'energy can neither be created (produced) nor destroyed by itself. It can only be transformed.' All of this I presume to build on the idea of a closed system naturally but under that assumption it makes good sense to me. then we come to 'In quantum mechanics energy is expressed using the Hamiltonian operator. On any time scales, the uncertainty in the energy ... is similar in form to the Heisenberg uncertainty principle (but not really mathematically equivalent thereto, since H and t are not dynamically conjugate variables, neither in classical nor in quantum mechanics).

So, how am I supposed to understand this. Is this a suggestion that an atom is on that indeterminate 'scale' that it gets its 'energy' from HUP (Heisenberg Uncertainty Principle)? And as HUP is outside Planck scale it is free to violate times arrow, which means that all bets on an atoms energy is open to interpretation? And if so, what regulates that 'energy' to a 'consistent system' differing for different atoms under our arrow of time.

Don't know if I made this clear enough, but I hope you can follow it?

You have to remember that when I'm looking at it, I differ between the 'arrow of time' and 'time' in itself. 'Time' is what exist, like a pool of undifferentiated water, where the stream we see will be our 'arrow of time' defining us macroscopically.