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Homework Help: Electron scattering: nuclear radius to nucleon number relationship

  1. Sep 15, 2013 #1
    Hi! I am extremely confused on what seems to be quite a simple question. The question contains a graph of root mean square radius <r[itex]^{2}[/itex]> plotted against A[itex]^{1/3}[/itex] where A is the nucleon number. In the lecture notes he specifies that <r[itex]^{2}[/itex]> is not the same as R but does not really say specifically what the difference is. It is given that the gradient of the line in this graph is 0.96. I am meant to find the value of R[itex]_{0}[/itex] in the relationship R=R[itex]_{0}[/itex]A[itex]^{1/3}[/itex] but I'm not certain how to find it because I dont know what the relationship between the rms r and R is.

    Any help would be amazing.

    I have worked through trying to use the charge radius but without success, he never mentioned the charge radius in the lecture so I'm not sure what to do. http://en.wikipedia.org/wiki/Charge_radius

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  3. Sep 15, 2013 #2


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    If you have a uniform sphere of radius R, what is the (squared) rms radius <r2> of its volume? Hint: You'll need an integral (or a formula).
  4. Sep 15, 2013 #3
    Thanks so much I think I'm on the right track now. So for a uniform sphere you use some spherical coordinate integrals to find that the rms radius is related to the radius by [itex]\frac{3}{5}[/itex]R[itex]^{2}[/itex]. Is this the correct formula to get?

    Also am I right in saying that I am effectively finding the expectation value of r[itex]^{2}[/itex]?
  5. Sep 15, 2013 #4
    Finally got the answer! Thanks again man couldn't have done it without you!
  6. Sep 15, 2013 #5


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