Cooling Atoms to Millionths of 1 Degree by Laser?
[caption id="attachment_24362" align="alignright" width="480"] Laser trapped erbium atoms. Image by NIST[/caption] Laser cooling refers to a variety of techniques. The most common method is Doppler laser cooling. But cooling atoms by laser? Although the math and physics are challenging, we can understand the idea and basic mechanism more easily when we introduce three basic concepts first: quantum absorption of energy, the Doppler effect, and how atomic motion correlates with temperature. The Absorption of Energy "Quanta" It is at the very heart of the quantum theory that an electron bound in an atom cannot absorb just any amount of energy it encounters. In the free state, it can, but as soon as the electron is restrained as part of a new structure in an orbital, only certain discrete amounts of energy…