Editing Rutherford scattering experiments (section)

===Alpha particle scattering: 1906 and 1908 experiments===
Rutherford's first steps towards his discovery of the nature of the atom came from his work to understand alpha particles.<ref name=Baily2013/>{{rp|17}}<ref name="Barrette2021"/>{{rp|435}}
In 1906, Rutherford noticed that alpha particles passing through sheets of mica were deflected by the sheets by as much as 2 degrees. Rutherford placed a radioactive source in a sealed tube ending with a narrow slits followed by a photographic plate. Half of the slit was covered by a thin layer of mica. A magnetic field around the tube was altered every 10 minutes to reject the effect of beta rays, known to be sensitive to magnetic fields.<ref name=LeoneRobotti2018>{{Cite journal |last1=Leone |first1=M |last2=Robotti |first2=N |last3=Verna |first3=G |date=May 2018 |title='Rutherford's experiment' on alpha particles scattering: the experiment that never was |url=https://iopscience.iop.org/article/10.1088/1361-6552/aaa353 |journal=Physics Education |volume=53 |issue=3 |pages=035003 |doi=10.1088/1361-6552/aaa353 |bibcode=2018PhyEd..53c5003L |issn=0031-9120|url-access=subscription }}</ref> The tube was evacuated to different amounts and a series of images recorded. At the lowest pressure the image of the open slit was clear, while images of the mica covered slit or the open slit at higher pressures were fuzzy. Rutherford explained these results as alpha-particle scattering<ref name=Heilbron1968/>{{rp|260}} in a paper published in 1906.<ref name=Rutherford1906a>{{Cite journal |last=Rutherford |first=E. |date=August 1906 |title=XIX. Retardation of the α particle from radium in passing through matter |url=https://zenodo.org/records/1430810 |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |language=en |volume=12 |issue=68 |pages=134–146 |doi=10.1080/14786440609463525 |issn=1941-5982}}</ref> He already understood the implications of the observation for models of atoms: "such a result brings out clearly the fact that the atoms of matter must be the seat of very intense electrical forces".<ref name=Rutherford1906a/>{{rp|145}}<ref name="Baily2013">{{Cite journal |last=Baily |first=C. |date=January 2013 |title=Early atomic models – from mechanical to quantum (1904–1913) |url=http://link.springer.com/10.1140/epjh/e2012-30009-7 |journal=The European Physical Journal H |language=en |volume=38 |issue=1 |pages=1–38 |doi=10.1140/epjh/e2012-30009-7 |arxiv=1208.5262 |bibcode=2013EPJH...38....1B |issn=2102-6459}}</ref>

{{anchor|1908 experiment}}
[[File:Geiger1908.jpg|upright=1.5|thumb|This apparatus was described in a 1908 paper by Hans Geiger.  It could only measure deflections of a few degrees.]]
A 1908 paper by Geiger, ''On the Scattering of α-Particles by Matter'', describes the following experiment. He constructed a long glass tube, nearly two metres long.  At one end of the tube was a quantity of "[[Radon-222|radium emanation]]" (R) as a source of alpha particles.<ref name=Baily2013/>{{rp|20}}  The opposite end of the tube was covered with a phosphorescent screen (Z).  In the middle of the tube was a 0.9&nbsp;mm-wide slit.  The alpha particles from R passed through the slit and created a glowing patch of light on the screen.  A microscope (M) was used to count the scintillations on the screen and measure their spread.  Geiger pumped all the air out of the tube so that the alpha particles would be unobstructed, and they left a neat and tight image on the screen that corresponded to the shape of the slit.  Geiger then allowed some air into the tube, and the glowing patch became more diffuse.  Geiger then pumped out the air and placed one or two gold foils over the slit at AA.  This too caused the patch of light on the screen to become more spread out, with the larger spread for two layers.<ref name=Baily2013/>{{rp|20}}   This experiment demonstrated that both air and solid matter could markedly scatter alpha particles.<ref name=Geiger1908>[[#refGeiger1908|Geiger (1908)]]</ref><ref name=Baily2013/>{{rp|20}} 
{{Clear}}