= Geiger-Marsden angular-scattering experiment of 1913
{c}
The later angular test used an evacuated chamber with a <radon> source and scattering foil fixed in place. A diaphragm served as a <collimator>; a <zinc sulfide> screen and attached <optical microscope> rotated about the foil on a graduated platform. <Particle scintillation> counts sampled successive <angles>. Foil-out counts supplied <background subtraction>, with corrections for source <radioactive decay> and finite beam width. Shielding reduced interfering radiation, but screen glow limited large <angles>. This tested the <Rutherford differential cross-section>.<The Laws of Deflexion of Alpha Particles through Large Angles by Hans Geiger and Ernest Marsden>[The Laws of Deflexion of α Particles through Large Angles, transcription PDF pp. 3–7, Variation of Scattering with Angle, Fig. 1 and Tables I–II]{ref}
\Image[/geiger-marsden-fixed-and-rotating-detectors.png]
{title=Fixed backscattering screen and later rotating angular detector}
{description=Original schematic distinguishing the 1909 shielded reflection arrangement from the 1913 evacuated angular arrangement. Arrows indicate example particle paths, not calculated trajectories; component sizes and distances are schematic. The later screen and microscope rotate together while the source and foil remain fixed.}
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