The structure of CO on the Pt(112) stepped surface—a sensitive view of bonding configurations using electron stimulated desorption

TLDR: In this paper, the structure of chemisorbed CO on the steps of Pt(112) {Pt[3(111)×(001)]} was monitored as a function of coverage by the digital electron stimulated desorption ion angular distribution method (ESDIAD), digital low-energy electron diffraction (LEED), and temperature-programmed Desorption (TPD).

Abstract: The structure of chemisorbed CO on the steps of Pt(112) {Pt[3(111)×(001)]} was monitored as a function of coverage by the digital electron stimulated desorption‐ion angular distribution method (ESDIAD), digital low‐energy electron diffraction (LEED), and temperature‐programmed desorption (TPD). The ESDIAD method applied to the desorption of an electronically excited, neutral CO species (the metastable a3 π‐CO state) avoids the influence of image potential effects on the trajectory of desorbing species, yielding true desorption angles, equivalent to Pt‐CO bond orientations. CO adsorbs exclusively on step sites at low coverage with a 20° ‘‘downstairs’’ tilt from the [112] direction (designated ‘‘0°’’). LEED indicates (2×n) order (i.e., two‐fold order along the steps but no order up/down the steps) exists when the steps are half‐filled (about 0.19 ML). At 0.24 ML, CO is still adsorbed only on the step sites but one‐dimensional CO–CO repulsions between nearest neighbors result in CO tilting along the steps. T...