Alpha Decay PhET

Directions:

1. Click Here to run the PhET

2. On the tabs - click "Single Atom" and hit pause. If your atom decays before you hit pause, just click "Reset Nucleus"

3. Initially, you will see the energized Parent nucleus (Po-211) The Alpha particles are confined in the nucleus by the blue potential well (Strong Nuclear force). The only way they can actually escape is to violate (briefly) conservation of energy. This process is called "Quantum tunneling" with the idea that the particles somehow tunnel through the barrier. Since the conjugates of energy and time are uncertain, if we wait long enough, this will happen - the alpha particle will "borrow" energy from the vacuum, as we say, just long enough to escape. The escaped particle doesn't have enough energy to have escaped over the top of the blue PE barrier, so we say it "tunneled". What really happened was a quantum transition.

4. Click the "Play button and watch the nucleus decay from Po-211 to Pb-207. Notice that this decreases the energy level to the point that a nuclear decay would involve a long term violation of conservation of energy (i.e. the particles in the nucleus have a negative energy)

5. Reset the Nucleus a few times, and notice that the time of decay is highly variable. (I have had some happen before I can hit pause, and some take longer than the graph can graph) This is because we are looking at one atom.

Isn't that neat?