(2) at higher coverages, the atomic site is still dominant but less so; (3) the spectroscopy is modified by CO-CO interactions via coupling of adjacent molecules, which can be detected for both occupied states and the LUMO. Conclusion (3) is new, while experimental findings have also drawn conclusions (1) and (2), albeit imprecisely. Finally (4) binding of CO pairs into an OCCO molecule appears to have a marked effect on the spectroscopy but may not be energetically favorable, based on (admittedly unreliable) DFT theory. Correlating site positions to photoemission data can be useful in other contexts. Other low-index facets of Cu (100) and Cu (110) and higher-index facets such as Cu (711) and Cu (210) are often considered highly reactive for specific CO2 products. 3 Cu (110) and Cu (210) exhibit Faradaic efficiencies of circa 50% or higher for methane production; Cu (711) and Cu (100) in contrast hover at circa 40% or higher for ethylene production. 3 Both low-index and higher-index facets feature different atomic packing than (111); (110) and higher index facets often feature bridging, kinked, or terraced facets whereas (100) is planar but less compact than (111). Greater characterization and accurate prediction of the properties of these interfaces can identify and inform the spectra and selectivity observed in experiment.