Exploring Atom-Laser Interactions: Understanding the Role of Photons

[Niles]

Hi

I have two questions regarding atom-light interaction.

1) Usually when we look at e.g. slowing atoms by a laser beam, we model the atom as a classical particle, i.e. we deal with a force F and not an operator. I was wondering why we are allowed to do that. Is it because the atom is small compared to the distancve over which the intensity of the beam changes?

2) Is it correct to say that as long as we have *many* photons, then the particular light beam we look at can be described classically? I know I haven't quantified what "many" is, but I hope the idea is clear.Niles.

 

[BigJDubs]

1) Yes, you are correct. The atom is so small that the intensity of the laser beam can be assumed to remain constant over the atom's size. This allows us to model the atom as a classical particle and use classical equations to describe its motion. 2) Yes, it is generally true that if there are many photons in a particular light beam then it can be described classically. However, since the exact number of photons needed for this to be true can vary depending on the nature of the light beam, it is difficult to provide an exact number.