Does Pair Production Take Place in Vacuum?

A further condition which must be satisfied during the pair-production process: conservation of momentum. Pair formation however, unlike pair annihilation, cannot occur in a vacuum or empty space.

This is due to the fact that in empty space, such a mechanism does not conserve both energy and linear momentum. To conserve these quantities, one needs to be near the field of an atomic nucleus which can absorb some of the recoil; something must absorb the momentum (p=h/l =hf/c) of the initial photon.

p/s : The video is too long. You can adjust the video speed if you want 😊