Non-adiabatic processes in adsorption/desorption phenomena

The coupling between electronic and nuclear motions, which is neglected in the adiabatic approximation, allows energy flow between the two sorts of motion. In chemisorption systems, such energy flow is a non-adiabatic effect which has several consequences; among them are the broadening of the IR vibration line of a chemisorbed atom, and the possibility of a gas-phase atom losing enough energy to stick on to the substrate. In this paper model calculations are reported which indicate that IR linewidths and sticking coefficients due to non-adiabatic effects can be important.