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Incoming links: Ernest Rutherford
In 1932 John Douglas Cockcroft and Ernest Thomas Sinton Walton accelerated hydrogen ions from a discharge source through an evacuated tube onto lithium at . A side-facing zinc sulfide screen, viewed by microscope, showed particle scintillations. Mica stopped scattered protons; switching off or blocking the beam removed the flashes. An external screen allowed absorption-range measurements.[ref]
Experiments with High Velocity Positive Ions. II. The Disintegration of Elements by High Velocity Protons by John Douglas Cockcroft and Ernest Thomas Sinton Walton. Experiments with High Velocity Positive Ions. II. The Disintegration of Elements by High Velocity Protons, 1932, pp. 230–232, sections 2–3, Fig. 1; primary text inspected in the Scribd transcription
Magnetic deflection checked voltage calibration. Opposite screens and independent observers found excess coincidences for a thin lithium target, supporting paired alpha particle emission; geometry and screen efficiency limited detection.[ref]
Experiments with High Velocity Positive Ions. II. The Disintegration of Elements by High Velocity Protons by John Douglas Cockcroft and Ernest Thomas Sinton Walton. pp. 231, 237–238, section 4, Figs. 5–6: corrected voltage calibration, paired screens and random-coincidence comparison
John Douglas Cockcroft's 1951 lecture recalls detection at and an absorption range about , then refined alpha particle energies about each. He places the work under Ernest Rutherford's direction. The inferred nuclear reaction was lithium-7 plus a proton producing two alpha particles.[ref]
Experiments on the interaction of high-speed nucleons with atomic nuclei by John Douglas Cockcroft. Experiments on the interaction of high-speed nucleons with atomic nuclei, lecture delivered 11 December 1951, pp. 167–170, Figs. 2–4; primary text inspected in the Scribd transcription
The logic has several independent links. Beam blocking tests whether the flashes depend on bombardment. An absorber tests whether scattered beam particles could reach the screen. A particle range tests product identity and kinetic energy, while coincidences test whether two products belong to one event. These tests support a reaction interpretation jointly; counting flashes alone is not an isotope identification, and a range-to-energy conversion needs calibration. The lithium proton reaction energy below is a modern calculation, separate from those historical measurements.
Ernest Rutherford 2026-10-18
A physicist.[ref]
https://www.physics.manchester.ac.uk/about/history-and-heritage/. Independent biographical identity and professional specialization
Portrait of Ernest Rutherford
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The Rutherford scattering model connects large-angle deflections to concentrated electric charge. The Geiger-Marsden experiment supplies the experimental context; a predicted angular distribution needs comparison with detector geometry and background counts.
Geiger-Marsden experiment 2026-10-18
The Geiger-Marsden experiment probes the interior of a chemical atom by counting alpha particles deflected by metal foils. The surprising observation was a small population returning towards the incident side. Hans Geiger and Ernest Marsden performed the experiments under Ernest Rutherford's direction; Ernest Rutherford developed the Rutherford model in 1911. Observation and interpretation were distinct contributions.[ref]
Marsden, Ernest by Ross Galbreath. Dictionary of New Zealand Biography; Biography, paragraphs on the 1909 undergraduate experiment and subsequent interpretation
In 1909, a radon source and its radioactive decay products in a conical glass tube supplied alpha particles through a mica window towards a reflector. Lead shielded a fixed zinc sulfide screen from direct hits; an optical microscope resolved individual particle scintillations. Reflectors occupied the same position. Reflector-out counts tested air scattering; stacked gold foils and bare glass tested thickness and support contributions.[ref]
On a Diffuse Reflection of the Alpha-Particles by Hans Geiger and Ernest Marsden. On a Diffuse Reflection of the α-Particles, printed pp. 495–498, Fig. 1 and experiments I–II
Nearby source geometry blurred incidence angles. Extrapolating platinum counts uniformly over a hemisphere was an assumption, not a universal reflection probability.[ref]
On a Diffuse Reflection of the Alpha-Particles by Hans Geiger and Ernest Marsden. Printed pp. 497, 499–500, angular limitation and experiment III
By Hans Geiger and Ernest Marsden. Proceedings of the Royal Society A 82, 495–500 (1909). Communicated by Ernest Rutherford; INFN hosts the transcription.
Rutherford model 2026-10-18
The Rutherford model places a concentrated central electric charge inside a much larger chemical atom. In 1911, Ernest Rutherford argued that rare large deflections were predominantly single close encounters, rather than accumulated small deviations in a diffuse-charge atom. He treated the central electric charge as positive for calculation while noting that the scattering deductions did not establish its sign. He explicitly deferred atomic stability.[ref]
The Scattering of Alpha and Beta Particles by Matter and the Structure of the Atom by Ernest Rutherford. The Scattering of α and β Particles by Matter and the Structure of the Atom, §§1–3, printed pp. 669–675
The physical inference is a compact region generating a strong electric field, not a miniature hard wall. Most impact parameters miss that region, while a small subset give large deflections. The model supplies a way to infer interior structure from outgoing angles, a central use of scattering throughout atomic physics and nuclear physics. This inference does not by itself specify Electron quantum states or explain spectral lines.
The repulsive model also sets a probing scale. At closest approach, conservation of energy with zero radial velocity givesFor the numerical model above, even a head-on projectile turns at . This is a calculated closest-approach distance, not a measured atomic nucleus radius. A point-charge fit can constrain how compact the scattering centre must be, but cannot directly resolve structure at distances the projectiles never reach.
The Rutherford differential cross-section must not be extrapolated to zero angle: the unscreened point model has a forward divergence, while real neutral chemical atoms exhibit the screening effect, finite beam acceptance, and accumulated small deflections. At very short separation, finite nuclear size and the nuclear force can change the interaction. Nuclear recoil changes the relation between laboratory and centre-of-mass angles for lighter targets; appreciable energy loss or repeated large deflections invalidates the simple thin-foil scattering counts. These limits delimit the calculation rather than supplying evidence for a nuclear contact collision in the early experiment.
By Ernest Rutherford. Philosophical Magazine, series 6, 21, 669–688 (1911). ChemTeam hosts the inspected transcription.