Doppler cooling is a mechanism that can be used to trap and slow the

motion In physics, motion is the phenomenon in which an object changes its position with respect to time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed and frame of reference to an observer and mea ...

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas ...

s to cool a substance. The term is sometimes used synonymously with

laser cooling Laser cooling includes a number of techniques in which atoms, molecules, and small mechanical systems are cooled, often approaching temperatures near absolute zero. Laser cooling techniques rely on the fact that when an object (usually an atom) ...

, though laser cooling includes other techniques.

History

Doppler cooling was simultaneously proposed by two groups in 1975, the first being

David J. Wineland David Jeffrey Wineland (born February 24, 1944) is an American Nobel-laureate physicist at the National Institute of Standards and Technology (NIST) physics laboratory. His work has included advances in optics, specifically laser-cooling trap ...

and Hans Georg Dehmelt and the second being

Theodor W. Hänsch Theodor Wolfgang Hänsch (; born 30 October 1941) is a German physicist. He received one-third of the 2005 Nobel Prize in Physics for "contributions to the development of laser-based precision spectroscopy, including the optical frequency comb t ...

and

Arthur Leonard Schawlow Arthur Leonard Schawlow (May 5, 1921 – April 28, 1999) was an American physicist and co-inventor of the laser with Charles Townes. His central insight, which Townes overlooked, was the use of two mirrors as the resonant cavity to take maser act ...

. It was first demonstrated by Wineland, Drullinger, and Walls in 1978 and shortly afterwards by Neuhauser, Hohenstatt, Toschek and Dehmelt. One conceptually simple form of Doppler cooling is referred to as

optical molasses