I am reading an article in a popular science magazine about atoms in extremely low temperature (condensation?). It's interesting and I've got few questions regarding this phenomenon.
1) In the article, the author show an figure of how the atom looks like in momentum space (like the top figure here). I'm pretty confused at how people measure the momentum of the atom? By light? I remember in the text, it introduced in one chapter how people shine a line on a material, and collect the emitted light, compare how the light intensity is reduced so as to be able to estimate the number of atoms there are. But does this method work for momentum estimation too?
2) I remember in the lecture of quantum mechanics, even at absolute-zero temperatures, the atoms won't be still, it has something called zero-point energy, so does it mean that the atom will be vibrating even at zero kelvins? So in the top figure here, we can observe that the momentum distribution has width about the peak, is that width telling us there will be some atoms moving at different momenta or the width is due to the uncertainty? So what does the distribution of momentum look like in absolute zero temperature?
3) The last question is in the article, the author said the momentum distribution is a Gaussian. But I searched in the library, they said for Boson, the condensation satisfies Bose-Einstein distribution. So what is the physical origin to use Gaussian distribution instead?