Question 3.3: Suppose that we fire a beam of alpha particles at an atomic ......

Introduction to Nuclear Reactor Physics [1368692]

Suppose that we fire a beam of alpha particles at an atomic nucleus and we find that some of the alpha particles are scattered at an angle of greater than 90°. What can be concluded from this simple observation?

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If some of the alpha particles are scattered back at an angle of greater than 90°, we must conclude that the velocity of the alpha particles is negative, and from Equation 3.51, we must conclude that A > 4. In other words, the atomic nucleus must have a mass greater than that of the incoming alpha particles.

$\mathbf{A}={\frac{4\left(\mathbf{V}_{\alpha}-\mathbf{V}_{\alpha}^{\prime}\right)}{\left(\mathbf{V}_{\alpha}+\mathbf{V}_{\alpha}^{\prime}\right)}}$ (3.51)

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