Ultracold atom

Ultracold atom

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Ultracold atoms is a term used to describe atoms that are maintained at temperatures close to 0 kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

s (absolute zero
Absolute zero
Absolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means....

), typically below some tenths of microkelvins (µK) (at 1.7 × 10−7 K the first Bose-Einstein condensation was observed), where their quantum-mechanical properties become important. In other words, the atoms are so cold that they can no longer be thought of as classical billiard balls. Usually, one finds this term used in research related to the production of the above-mentioned Bose-Einstein condensates. Key methods to produce ultracold atoms are laser cooling
Laser cooling
Laser cooling refers to the number of techniques in which atomic and molecular samples are cooled through the interaction with one or more laser light fields...

 and evaporative cooling.

Examples

  • The melting point for helium
    Helium
    Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

     is 0.95 kelvin.
  • The largest cluster of francium
    Francium
    Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K.Actually the least unstable isotope, francium-223 It has the lowest electronegativity of all known elements, and is the second rarest naturally occurring element...

    was made from 10,000 ultracold atoms.