Not sure if this question belongs in particle physics but I figured it was a good place to start. I've been having an on going discussion about the nature of the electron and came to the question, can an electron literally be captured? IE can you slow a free electron to the point that its position can always be determined? Can an electron be stopped? I dont know that it can, but it's always nice to be wrong. Furthermore, is there a relation between electron rest mass and its momentum in a basic hydrogen atom (1s)?