Geiger, Hans, John Harling & Ernest Marsden. “On the Diffuse Reflection of the α-Particles"

First edition, first impression of one of the five key papers resulting from Ernest Rutherford’s landmark gold foil experiment, which led to the modern understanding of atomic structure. An attractive copy and uncommon in the original journal format, as here.

During the early years of the 20th century physicists had a poor understanding of the structure of atoms, whose existence had only been proved mathematically by Einstein in 1905. The leading — though still controversial — theory was J. J. Thomson’s “plum pudding” model, which posited that the mass of an atom was evenly distributed, with negatively charged electrons appearing throughout like raisins in a Christmas pudding. If that were the case, alpha particles emitted by radioactive substances should pass through atoms with little or no deflection. But in an elegant series of experiments Ernest Rutherford, Hans Geiger, and Ernest Marsden showed that they were often deflected, sometimes by more than 90 degrees, as described here in “On the Diffuse Reflection of the α-Particles”. Rutherford used the results of these experiments to mathematically model the alpha scattering, proving that atoms contained a dense, positively charged nucleus surrounded by negatively charged electrons with little mass, publishing this conclusion as "The Scattering of α and β Particles by Matter and the Structure of the Atom" in 1911.