Quantum state and surface-site-resolved studies of methane chemisorption by vibrational spectroscopies

The combination of quantum state-specific reactant preparation by infrared laser pumping with surface-site-resolved detection of chemisorbed reaction products by Reflection Absorption Infrared Spectroscopy (RAIRS) enables highly detailed studies of molecule/surface reactivity. In this perspective, we review the methodologies developed for simultaneous quantum state- and surface-site-resolved reactivity measurements and their application towards the chemisorption of methane on stepped and kinked platinum surfaces. We demonstrate that RAIRS allows for surface-site-resolved detection of methane dissociation, which serves to measure surface-site-resolved product uptake curves, sticking probabilities, and dissociation barrier heights. For the dissociation of C-H stretch excited singly deuterated CH3D on a stepped Pt surface such as Pt(211), RAIRS was used to detect bond selectivity in methane chemisorption and to reveal how the bond-selective dissociation proceeds from the step to the terrace sites with increasing incident kinetic energy of the CH3D reactant. Extension to site-selective RAIRS detection of methane dissociation to other vicinal surfaces such as Pt(210), Pt(531), and Pt(110)-(2x1) are also presented.