Now, laser to cool down molecules

Cooling molecules is much trickier than chilling individual atoms.

London: Scientists have apparently succeeded in cooling a dipolar molecule just a fraction of a degree above absolute zero (around -273 degrees Centigrade) with the help of lasers.

This may be an important step to generate new kinds of ultra-cold matter that could be used for everything from quantum computing to chemistry.

Edward Shuman, John Barry and David DeMille, all from Yale University used an old technique and several new tricks to cool molecules of strontium monofluoride (SrF) to just a few hundred microkelvin.

DeMille and colleagues wanted to try to cool molecules rather than atoms, allowing them to study the quantum-mechanical nature of chemistry.

Cooling molecules is much trickier than chilling individual atoms. Molecules are heavier than atoms, which make them less responsive to laser light.

First, the scientists chose SrF, a molecule that calculations showed was unlikely to start vibrating and thereby hinder the cooling process. They picked a colour of laser light that ensured the energy absorbed by the molecules would not set them spinning.

Finally, the team used a new source of molecules that pre-cooled the SrF better than had been done before.

"It worked better than we expected, and as fast as we could have possibly hoped," Nature quoted DeMille as saying.

The team managed to get their SrF molecules chilled to around 300 microkelvin in one direction.

"The temperatures that he was able to achieve were not spectacularly low," said Jun Ye, of JILA in Boulder, Colorado.

But he added that the ability to apply the technique to a range of molecules makes it exciting: "If laser cooling works, it potentially allows many different molecules to be put into the ultra cold regime."

The findings were published in the journal Nature1.


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