Low-energy electron-induced chemistry of ethylene on clean and chlorine- and deuterium-covered silver(111)

Switching from molecular to dissociative adsorption with vibrational energy: ethylene on Ag(001)

“…Moreover, the spectra reported in the literature for the possible fragments do not match the observed losses. In particular the vibrational spectrum of vinyl, whose formation was suggested by Zhou and White [14], was measured for adsorption on Ni(0 0 1) [21] and exhibits a doublet at 114 and 95 meV, corresponding to the wagging modes of the CH 2 and CH groups, respectively, with twist (145 meV), rock (160 meV) and scissor (176 meV) modes of comparable intensity, contrary to our experimental result. Moreover the CH stretch of vinyl has two components at 365 and 386 meV, which are not observed in our case.…”

“…Comparing such frequencies with those reported for gas phase molecules and for ethylene adsorption on Ag(1 1 0) [13] and taking the isotopic shifts into account we assign the modes, respectively, to the molecule±surface stretch, to the wagging and to the CH stretch motion of pbonded C 2 H 4 . The assignment is con®rmed by the observed desorption temperature of 140 K, typical of this moiety on Ag [13,14]. The loss frequencies are summarised in Table 1.…”

“…3) indicating that, in addition to the p-bonded species, another more strongly bonded moiety has formed (the loss at 117 meV, a signature of the p-bonded species, is covered by the doublet structure). Zhou and White [14] observed a C 2 H 4 desorption peak at around 200 K on Ag(1 1 1) after heavy irradiation of p-bonded ethylene with electrons. The higher desorption temperature was explained with the formation of either di-r-bonded ethylene or vinyl (CH±CH 2 ).…”

Chemically Induced Electronic Excitations at Metal Surfaces

“…Figure 2B shows the carrier detection efficiency from C 2 H 6 , C 2 H 4 , C 3 H 8 , CO 2 , Xe, and N 2 O. Low detection efficiencies and minimal signal decay were observed and were consistent with the relatively low E ads and relatively rapid desorption rates of these species on Ag (15)(16)(17)(18)(19)(20). Studies of C 2 H 6 and C 2 H 4 interactions with single-crystal Ag have measured adsorption energies of 0.25 for C 2 H 6 (15, 16 ) and 0.33 eV for C 2 H 4 (17 ).…”

Mimicking Aspects of Heterogeneous Catalysis: Generating, Isolating, and Reacting Proposed Surface Intermediates on Single Crystals in Vacuum

“…84,113 There are also examples in the literature where electrons have been used to selectively dissociate carbon-halogen bonds in halohydrocarbons (see "e" under techniques in Table 4). With respect to spectroscopic identification of these fragments it is desirable (for avoiding spectral interference) that the molecular precursor be chosen so that it may be thermally desorbed from the surface at temperatures below where the fragment of interest decomposes.…”