Editing Superfluid helium-4 (section)

== Applications ==
Recently{{timeframe|date=September 2024}} in the field of chemistry, superfluid helium-4 has been successfully used in [[spectroscopic]] techniques as a [[quantum solvent]]. Referred to as superfluid helium droplet spectroscopy (SHeDS), it is of great interest in studies of gas molecules, as a single molecule solvated in a superfluid medium allows a molecule to have effective rotational freedom, allowing it to behave similarly to how it would in the "gas" phase.  Droplets of superfluid helium also have a characteristic temperature of about 0.4&nbsp;K which cools the solvated molecule(s) to its ground or nearly ground [[Rovibronic coupling|rovibronic]] state.

Superfluids are also used in high-precision devices such as [[gyroscope]]s, which allow the measurement of some theoretically predicted gravitational effects (for an example, see [[Gravity Probe B]]).

The Infrared Astronomical Satellite [[IRAS]], launched in January 1983 to gather infrared data was cooled by 73 kilograms of superfluid helium, maintaining a temperature of {{convert|1.6|K|C}}. When used in conjunction with helium-3, temperatures as low as 40&nbsp;mK are routinely achieved in extreme low temperature experiments. The helium-3, in liquid state at 3.2&nbsp;K, can be evaporated into the superfluid helium-4, where it acts as a gas due to the latter's properties as a Bose–Einstein condensate. This evaporation pulls energy from the overall system, which can be pumped out in a way completely analogous to normal refrigeration techniques. (See [[dilution refrigerator]])

Superfluid-helium technology is used to extend the temperature range of [[cryocoolers]] to lower temperatures. So far the limit is 1.19&nbsp;K, but there is a potential to reach 0.7&nbsp;K.<ref>{{cite book|last1=Tanaeva|first1=I. A.|title=AIP Conference Proceedings|date=2004|volume=710|chapter=Superfluid Vortex Cooler|issue=3 |pages=034911–1/8 |doi=10.1063/1.1774894|s2cid=109758743 |url=https://pure.tue.nl/ws/files/1719607/Metis192474.pdf |chapter-url=https://research.tue.nl/nl/publications/the-superfluid-vortex-cooler(422e0405-c46f-4eb5-8088-2fc2689972b4).html}}</ref>