Vibrationally bond-selected chemisorption of methane isotopologues on Pt(111) studied by reflection absorption infrared spectroscopy

Abstract

Reflection absorption infrared spectroscopy (RAIRS) was used to probe for vibrational bond-selectivity in the dissociative chemisorption of three partially deuterated methane isotopologues on a Pt(111) surface. While a combination of incident translational energy and thermal vibrational excitation produces a nearly statistical distribution of C–H and C–D bond cleavage products, we observe that laser excitation of an infrared active C–H stretch normal mode leads to highly selective dissociation of a C–H bond for CHD₃, CH₂D₂, and CH₃D. Our results show that vibrational energy redistribution between C–H and C–D stretch modes due to methane/surface interactions is negligible during the sub-picosecond collision time which indicates that vibrational bond-selectivity may be the rule rather than the exception in heterogeneous reactions of small polyatomic molecules.