Understanding the Effect of an Amorphous Surface on the Ultrafast Dynamics of a Heterogeneous Photoinduced Reaction: CD 3 I Photoinduced Reaction on Amorphous Cerium Oxide Films.

In this work, to understand how an amorphous surface influences the dynamics of surface photoinduced reactions, pump-probe spectroscopy in conjunction with mass spectrometry is employed to track the ultrafast evolution of intermediates and final products with time, mass, and energy resolution. As a model system, the photoinduced reaction of CD 3 I adsorbed on amorphous cerium oxide films is investigated. A fraction of the first intermediates produced on a freshly prepared surface is trapped to passivate the surface. After the A-band excitation, the minimum dissociation time of CD 3 I indicates that CD 3 I adsorption geometries with either CD 3 or I facing the gas phase exist; however, the transient data suggest that most molecules are adsorbed with the I atom facing the surface. CD 3 and I are consumed to form I 2 and reform CD 3 I, which are produced at a steady rate only after the intermediates have lost the excess translational energy released from photodissociation.