Rutherford Spanking -

(also known as the Geiger-Marsden experiment). While "spanking" isn't a formal scientific term, it is often used colloquially to describe the dramatic way alpha particles "smacked" into the gold foil and, against all expectations, bounced backward. The Experiment

Rutherford’s team set up a lead screen with a small hole to create a beam of (positively charged helium nuclei). They fired this beam at an incredibly thin sheet of gold foil. rutherford spanking

A fluorescent screen that emitted a tiny flash of light (scintillation) when struck by an alpha particle. (also known as the Geiger-Marsden experiment)