The thermal chemistry of adsorbed ethyl on the Pt(111) surface: infrared evidence for an ethylidene intermediate in the ethyl to ethylidyne conversion

The reflection absorption infrared (RAIR) spectrum of the adsorbed ethyl (C 2H5) moiety produced by the dissociative adsorption of ethane from a supers onic molecular beam onto Pt(111) at 150 K is reported. The thermal chemistr y of the C2H5 fragment so produced was then followed using a combination of RAIR spectroscopy and temperature programmed desorption (TPD). The RAIR sp ectra indicate the presence of ethylidene (CHCH3) and ethylidyne (CCH3) at 250 and 350 K respectively. This implies the stepwise loss of one and two h ydrogen atoms from the ethyl moiety during the heating process. Temperature programmed desorption (TPD) measurements show that hydrogen desorption is not accompanied by desorption of either saturated or unsaturated C-2 hydroc arbons or methane into the gas phase.