Geiger-Marsden angular-scattering experiment of 1913 2026-10-18
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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.[ref]
Figure 1.
Fixed backscattering screen and later rotating angular detector
. 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. Details.
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Hans Geiger Created 2026-10-18 Updated 2026-11-05
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Hans Geiger and Ernest Marsden counted large-angle deflections of alpha particles from metal targets. Their 1909 work used visible scintillations to register particles scattered back toward the incident side, establishing that rare strong deflections required explanation. Their 1913 measurements tested the angular dependence more systematically with thin targets. Comparing count rates with target thickness, incident energy and observation angle helped turn the concentrated-charge picture of Rutherford scattering into a quantitative experimental test.[ref]
Figure 1.
Portrait of Hans Geiger
. Source.
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