Experimental evidence of vibrational selectivity in surface charge-transfer reactions

Surface (charge-transfer) reactions from polyatomic molecules adsorbed on metals have been investigated by infrared radiation. Examples of laser catalysis on adsorbed SF6, C3H3N (ACN) and CH3I on different surfaces are reported in which clear catalytic products were detected and analyzed. A detailed study of ACN adsorbed on Cu was carried out. Thus, the electron emission and CN− yield produced by laser irradiation of acrylonitrile (ACN) adsorbed on a polycrystalline Cu surface were investigated over the 930–953 cm−1 wavenumber range. Both emissions show a clear wavelength dependence with a≈20 cm−1 redshift with repsect to the gas-phase ACN spectrum. The laser catalysis CN− yield is discussed in light with both substrate and adsorbate mediated mechanisms, which seem to be controlling this (charge-transfer) surface reaction. Emphasis is made on the observed vibrational selectivity for this surface reaction.