• Drag your cursor across the screen to aim the crosshairs.
• Click the “Shoot” button.

What will happen?

• An electron will come shooting out from the bottom. If you are a good shot, and you figure out where to aim, you can try to dislodge the electron trapped in the first energy level of a hydrogen atom.
• Successfully dislodge the hydrogen electron from the hydrogen atom and you will earn credits you can use towards advancing your knowledge or winning prizes!

What you learn

• See what it looks like over very small timeframes with electrons and protons under the influence of the coulomb force.

A Proton (hydrogen atom) floating
away from a Methane (CH4) Molecule

How big and how fast?

• It takes less then one femtosecond to dislodge an electron. Protons are shown with a Bohr (53 picometers) radius and electrons with a Lorentz (3 femtometers) radius.
• Protons weigh 1836 times more then electrons. Protons are tracked on a femtosecond timescale, but electrons, being thousands of times lighter and faster, are tracked on an attosecond timescale.

Real time animations

• Electrons dont just sit and wait for you to shoot, when disturbed they move around, aim carefully.
• Try adding energy to your electron. More energy means more speed.
• Pause/Play button to stop and start.

Click to play “Free the Proton”

Energy and Speed

• The energy of an electron is measured in evolts and speed in picometers per attoseconds. For reference, the speed of light is 300 picos per attosecond.
• Using the formula E=½mv², 10eV = 1.9 picos/attosec, 100eV = 6.0 picos/attosec, 500eV = 13.4 picos/attosec

Now your a pro!

• The NIST maintains a database of ionization cross sections of molecules by electron impact, including H, He, and H². The cross sections are calculated using Binary-Encounter-Bethe (BEB) model.
• Their research shows that just under 100 eVolts of energy is best for knocking electrons out of hyrogen molecules, as the NIST link shows.