Adsorbate- versus substrate-mediated processes

When adsorbate molecules AB(ad) are irradiated with light, the following events may take place  

The probability of a particular event is expressed as a cross-section a, which depends on photon energy, adsorbate coverage, surface structure, surface composition, etc. The overall total cross-section of a surface photochemical process, (Ttot = dis + r+ cTdes. can be obtained from the slope of a semi-logarithmic plot of adsorbate concentration versus the incident photon fluence by assuming first-order (or pseudo- 

Laser Chemistry Spectroscopy, Dynamics and Applications Helmut H. TeUe, Angel Gonzalez Urena Robert J. Donovan 2007 John Wiley Sons, Ltd ISBN 978-0-471-48570-4 (HB) ISBN 978-0-471-48571-1 (PB) 

CH27 LASER STUDIES OF SURFACE REACHONS PHOTOCHEMISTRY IN THE ADSORBED STATE 

We would like to note that in this section, dedicated to the photochemistry of the adsorbate state, mainly two classes of processes are considered, namely photodissociation and photoreaction, which involve the breaking and making of chemical bonds, which are the basic elements of a chemical process. 

---