PHOTOCHEMISTRY OF C2H2 ON NACL(100)

Recent experiments show that the photochemistry of C2H2 on NaCl(100) is remarkably simple, producing only hydrogen/deuterium exchange: C2H2 + C2D2 reversible 2C2HD. A new mechanism of this surface bound reaction is proposed. We suggest that it is the substrate, NaCl, that absorbs the exciting 184.9 nm photons to produce self-trapped excitons (STE). The triplet STE then transfers its energy to adsorbed acetylene which then diffuses along the surface and reacts with its neighbours to achieve the hydrogen/deuterium exchange.