Kinetics of two-state chemisorption: Hydrogen on niobium

In the two-state model of chemisorption, it is assumed that there is a given density of chemisorption sites on the surface, each of which can exist in either of two states. The general rate equations were formulated and solved analytically under the assumption that the above two states are in local equilibrium. The kinetic equations describe accurately the photoemission data of Smith of hydrogen chemisorption on pure niobium. The analysis indicates that the two sites are tightly bound with a rather shallow ( approx. 5 kcal/mole H) barrier between them