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Homework Help: Geiger and Marsden experiment. How did they create a vacuum?

  1. Jun 28, 2011 #1


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    Hi, I would just like to know how did Geiger and Marden create a vacuum for alpha particles during the Rutherford scattering experiment? Also, when Rutherford discovered the alpha particle did he know it had +2e charge?

    Any help would be appreciated. I've looked everywhere for the answers but can't find them anywhere :(

  2. jcsd
  3. Jun 28, 2011 #2


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    I couldn't find out how they created the vacuum, but I suspect they just used a normal vacuum pump. It's not exotic technology, considering that it was invented in 1650.

    As for the alpha particles, he used a mass spectrometer to measure their charge to mass ratio. Since he got 0.5e/amu, he guessed that they were helium nuclei. To prove that they were actually helium nuclei, he trapped the ions, neutralized them, and analyzed the spectrum. See here: http://en.wikipedia.org/wiki/Alpha_particle#History_of_discovery_and_use
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