ABSTRACT
For RBS experiments, θ is usually chosen to be very close to 180°. From Equation 11.2, the highest scattered energy occurs for an infinite target mass M.
To obtain scattering rate information, we consider the forces acting between the colliding particles. For M >> m, the Rutherford scattering differential cross section is given by (Eisberg and Resnick, 1985)
(11.3)
d d
zZe E
σ Ω piε θ
=
1 4 4
1 20
4sin ( )/
where ze and Ze are the charges of the helium (z = 2) and target nucleus, respectively. The differential cross section dσ/dΩ is proportional to the number of helium nuclei that are scattered into a solid angle dΩ (Figure 11.1). Equation 11.3 is proportional to the square of the product of nuclear charges divided by the energy:
(11.4)
d d
zZ E
σ Ω ∼ ( )2
Another effect to be considered is the energy loss of the projectile during passage through a medium (Nicolet, 1979). Large energy losses from large-angle scattering, the basis of RBS, are rare compared to the numerous small energy losses that do not influence the trajectory appreciably.
