The dependence of the scattering characteristics of atoms on the energy of the collision can be modeled as follows. We suppose that the two colliding atoms behave as impenetrable spheres, as in Problem 18.16, but that the effective radius of the heavy atoms depends on the speed v of the light atom. Suppose its effective radius depends on v as Rze-"I", where v* is a constant. Take R, = t Rz for simplicity and an impact parameter b = t Rz' and plot the scattering angle as a function of

(a) Speed,

(b) Kinetic energy of approach.