OK, the idea of 0K as the temp between electron shells is compleatly absurd, no offence, but 0K is where no energy exist. And since there is energy between electron shells, the temp thus cannot be 0K. Now, according to einstein, space and time cannot be seperated. But if you are looking for 0K, look just inside the event horizon of a black hole, where space is isolated from time (thus no energy because things cannot move or change which requires energy) then there will be 0K, or no temp.