Sympathetic cooling

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Sympathetic cooling is a quantum optics technique in which particles of one type (1) are used to cool particles of another type (2). The particles of type (1) act as a heat bath for particles of type (2), the temperature of which is slowly lowered to the level of particles (1). The coupling takes place via collisions between the particles or, for example, in the case of ions through Coulomb interaction . The low-energy particles of type (1) thereby withdraw energy from the particles to be cooled (2).

The sympathetic cooling can be clearly compared with the cooling of a dish (e.g. some dessert creams) in an ice water bath.

The sympathetic cooling in particular extends the application range of laser cooling to those atoms that cannot be cooled directly. With this laser cooling of neutral atoms, the scattering of photons (from different directions) reduces the speed of the atoms. For this, however, a so-called closed transition is necessary, i.e. it must be possible to use a laser to lift the atom from a ground state to a specific excited state, from which it then falls back into the same ground state. The probability for the atom to leave this cycle in a dark state must therefore not be too great. If a closed transition is not available for an atom to be cooled, the method of sympathetic cooling can be used by introducing a second atom into the experiment, which can be cooled well with lasers and which then serves as a heat bath for the first type of atom .

Sympathetic cooling was demonstrated first for ions and later for atoms . With the similar electron cooling process , fast antiprotons at CERN were cooled by cold electrons.

Individual evidence

  1. ↑ D. Larson, J. Bergquist, J. Bollinger, Wayne Itano, D. Wineland : Sympathetic cooling of trapped ions: A laser-cooled two-species non-neutral ion plasma . In: Physical Review Letters . tape 57 , no. 1 , July 1986, ISSN  0031-9007 , pp. 70-73 , doi : 10.1103 / PhysRevLett.57.70 .
  2. ↑ C. Myatt, E. Burt, R. Ghrist, E. Cornell, C. Wieman : Production of Two Overlapping Bose-Einstein Condensates by Sympathetic Cooling . In: Physical Review Letters . tape 78 , no. 4 , 1997, ISSN  0031-9007 , pp. 586-58 , doi : 10.1103 / PhysRevLett.78.586 .
  3. ^ G. Gabrielse, X. Fei, L. Orozco, R. Tjoelker, J. Haas, H. Kalinowsky, T. Trainor, W. Kells: Cooling and slowing of trapped antiprotons below 100 meV . In: Physical Review Letters . tape 63 , no. September 13 , 1989, ISSN  0031-9007 , pp. 1360-1363 , doi : 10.1103 / PhysRevLett.63.1360 .