# Rutherford's gold foil experiment [duplicate]

Rutherford projected $\alpha$-rays onto the gold foil. $\alpha$-rays are the same as a $\ce{He^2+}$ nucleus and they can ionize atoms. Therefore, why are gold atoms not ionized when the $\alpha$-rays collide with them?

• Since electronic stopping (interaction of ions with electrons) is well known, the answer is the alphas did lose energy to electrons in the film. These low momentum interactions spread the beam. The spread of the transmitted beam was measured by Geiger and Marsden. – Jon Custer Jun 25 '17 at 16:30