Fig. 3: IR absorption spectroscopy and electron diffraction.

a TP-RAIRS (8 K per spectrum, low absorbance = blue, high absorbance = red) and b IR absorption spectra (Tsample = 90 K) during heating of C2H2ad/2Had adsorbed on Co(0001) in CO. The symmetric methyl bending mode (1352 cm−1) indicate that ethylidyne is present between 250 and 300 K. c LEED (80 eV) shows a c(4 × 2) pattern between 270 and 305 K, attributed to islands of an ordered ethylidyne/CO layer that cover up to 50% of the surface (pCO = 1 × 10−7 mbar, heating rate 0.2 K s−1, θC2Hx = 0.12 ML).