Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Don Kingsley on 08/02/2011 05:30:02
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Don Kingsley asked the Naked Scientists:
Why is rubidium used to produce the Bose Einstein condensate? Is it the only element that will work?
If so, why?
What do you think?
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I have never heard of rubidium being a Bose Einstein condensate. I know for sure that Helium-4 forms a Bose Einstein condensate.
Only bosons will form Bose Einstein condensates and the spin interactions of the nucleons in Helium-4 produce a Boson when super-cooled. I will look into Rubidium to see if and why it works.
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It seems that Rubidium also can be supercooled (to around 1.7×10−7 K which is minutely above absolute zero) to a state that is bosonic in nature. I'm not sure what other atoms can be supercooled into a boson, it has to do with how many neutrons and protons there are. These are both fermions which have a different spin than bosons and only form a boson due to the low thermal energy and the spin-spin interactions of the fermions.
For more information, look up Bose-Einstein condensates, bosons and fermions, and spin-spin interactions. Most of this could be found in a Thermal Physics book.
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First, BEC (Bose-Einstein Condensate) is a state of the matter, so all elements turn in to a BEC in his exclusive temperature and other conditions. Like water an alcohol have diferent booling points and helium 4 only get solid at high pressure and low temperature. My knoweldge is not enough to say if somebody has achived a bec with other materials, but i know certanily that the achivement of bec with rubidium, sodium and hydrogen is a reality.
bec video link:http://www.youtube.com/watch?v=eY6D2LjYKzw
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See a list of the elements used in successful demonstrations (http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate#Isotopes) of BEC.
Helium 4 demonstrates some of the properties of a BEC, but as a liquid, the adjacent atoms interact too strongly, and the BEC is actually formed as a dilute solution in a Helium 4 liquid which is mostly not a BEC.
Systems with half-integer spin are called Fermions, and cannot form a BEC. However, if you cool them down significantly, the Fermions can pair up (http://en.wikipedia.org/wiki/Fermionic_condensate), effectively forming a Boson, which then can form a BEC.
So electrons in some materials can pair up to form a BEC, which becomes visible as superconductivity.
In some cases, the half-integer spin of the nucleus, combined with the half-integer spin of the outer electron allows the atom as a whole to have a zero overall spin, and a single atom can act as a boson.
It is thought that quarks can also form a condensate (http://en.wikipedia.org/wiki/Fermionic_condensate#QCD), under some conditions.