image: Energy distribution of atoms in a thermal state. For positive absolute temperatures (upper part, blue), the low energy states have the highest population; for negative absolute temperatures, the high energy states are more occupied. This image relates to a paper that appeared in Jan. 4, 2013, issue of Science, published by AAAS. The paper, by Simon Braun at Ludwig-Maximilians-Universität München in Munich, Germany, and colleagues was titled, “Negative Absolute Temperature for Motional Degrees of Freedom.” view more
Credit: Image courtesy of LMU / MPQ Munich