1. Using conservation of energy and momentum perpendicular to the surface, derive the classical
expression for the energy exchange ΔE (Eq. (10.8)) when a gas phase species, mass mg, strikes a
surface cube, of mass ms, where μ = mg/ms, with a translational energy Ei along the surface normal.
2. Assuming a physisorption well can be represented by an attractive well of depth W followed by a
repulsive hard wall, show that the classical condition for trapping is given by Ei = 4μW/(1 - μ)2
(Eq. (10.9)).
3. Assuming that a molecule can be adsorbed only when its translational energy towards the surface is
greater than some critical value E0, i.e. S = 0 for E < E0 and S = 1 for E ≥ E0, derive an expression for
the average energy release along the surface normal 〈Ez〉 (Eq. (10.15)). Hence find the limiting behaviour
for a sticking threshold E0 = 0 or E0 » kBT. Hint use Eq. (10.13) to calculate 〈EP(E)〉/〈P(E)〉.
4. Assuming the adsorption probability S(E, θ) is unity about some critical normal energy E0 cos2θ, derive
the expression for the anticipated angular distribution P(θ, T) (Eq. (10.17)).
[Hint: This requires integrating Eq. (10.16) with appropriate limits for E(θ).]
Above Problems are available as a PDF to print
Solutions to Chapter 10 Problems