How does they check the number of atoms in BEC?

[Choi Si Youn]

In wikipedia, I read about BEC. so I just wonder in that articles, so I write in this page.
Adopt that article, " They did this by cooling a dilute vapor consisting of approximately
two thousand rubidium-87 atoms to below 170nK using a combination of laser cooling
and magnetic evaporative cooling."

So I just wonder How they check the "two thousand rubidium-87 atoms"?



It's my first time for writing in this forum, so maybe I choose wrong category.

but please, if you understand what I mean, answer under this writing.

 

[azntoon]

The number of rubidium-87 atoms can be counted using a technique known as atom counting. This technique involves counting the number of atoms in a sample by measuring the fluorescence emitted from the atoms as they are illuminated by a laser beam. The number of atoms is then calculated by measuring the intensity of the emitted light. This technique can be used to count the number of atoms in a sample with an accuracy of up to 1%.