Mode selective chemistry at surfaces

Surface chemistry experiments can now quantify the reactivity of polyatomic reagents prepared in select vibrational states. These studies of vibrationally mediated chemistry are showing that the nature of the vibrational excitation, and not just its total energy, can play an important role in determining the rates and pathways of surface reactions. Such vibrational mode selective behavior results when the timescale for statistical redistribution of vibrational energy within the reaction complex is slower than reaction. This review surveys prior examples of mode selective reactivity on surfaces, and it emphasizes four aspects of experimental work published within the past year: the extension of earlier methane/nickel studies to another metal, the observation of vibrational mode selectivity in a precursor-mediated reaction, the demonstration of bond-selective control over a gas–surface reaction, and the outline of an emerging framework for understanding the origin of these non-statistical reaction patterns in surface chemistry. These studies impact our fundamental understanding of surface chemistry, and they point toward new strategies for controlling and manipulating reactivity in vapor deposition processes.