Spatial distributions of desorption flow as an indicator for a precursor state in several systems

Spatial distributions of the desorption Row (SDDF) of CH4, N-2 and azometha ne (CH3N=NCH3) on molybdenum, O-2 and N-2 on iridium, and N-2 On iron were measured by TPD/TPR with angular resolution and described by the Comsa equa tion. The activation energy of chemisorption and the effect of the precurso r state on the total desorption rate were estimated from the parameters of the Comsa equation. The pathway via a precursor state is the main one (60-9 0%) for oxygen on iridium and for nitrogen and azomethane on molybdenum. Fo r other systems, this pathway cannot be completely excluded either. Accordi ng to our upper estimates, its contribution can be essential (similar to 40 %).