Interadsorbate interactions in the c(4×2) NO/Ni(111) system

Abstract

Electron energy loss spectroscopy has been used to map the dispersion of the dipole active internal NO stretch and of the NO frustrated translation, which has not been previously observed, in the c͑4ϫ2͒ NO/Ni͑111͒ system. The dispersion of the dipole active mode was fit with a model that assumed electrostatic dipole-dipole coupling ͑including image dipoles͒ between the adsorbates. The frustrated translation, on the other hand, showed no dispersion to within the resolution of the experiment across the entire surface Brillouin zone of the Ni͑111͒ substrate. These measurements reveal new information on interadsorbate interactions in an important model system.

A systematic review of the application of vibrational spectroscopy to the determination of the structures of NO adsorbed on single-crystal metal surfaces

“…In this and several other cases where [c(4 Â 2)] surface arrays have been recorded the wavenumbers are similar leading to the same structural assignment, viz., Ni ca. 1580; [9][10][11]13 Rh 1590, 17 and Pd 1620 23 or 1611. 20 DFT calculations on Pd at [c(4 Â 2)] 26 are consistent with the presence of both ccp and hcp forms of this species being present together.…”

“…However these weak bands are mostly recorded at higher coverage. On the various metals the n(MN) absorptions, with the corresponding n(NO) values given in brackets, have wavenumbers as follows: Ni 363 (1579); 13 Rh 360 (1530); 16 Pd 330 (1611); 20 Pt 306 (1515) cm À1 , 33 and 350 (1470) 34 cm À1. The data show that the 3-fold-hollow species can be expected to exhibit n(MN) bands between ca.…”

Coadsorbate effects on adsorbate vibrational properties

“…In our analysis the singleton frequencym single refers to the imaginary line position of an infrared active vibrational mode m for switchedoff dynamical dipole-dipole coupling [4,[12][13][14]. We note that the term 'singleton frequency' is not defined uniquely in the literature.…”

“…Two different meanings of the term singleton exist: first, it may refer to isolated species, isolated meaning adsorbed on an otherwise bare surface, i.e. with neither static, nor dynamical interactions acting on them [15,16]; second, it may correspond to an isolated species embedded in a layer of other (or identical) species, and with isolated meaning disregarding any dynamical interactions, but with static (chemical) interactions included [4,[12][13][14]. Only in the second case it may be used as a reference value to quantify dynamical lateral coupling; this is why we adhere to this interpretation.…”

Synergistic Promotion of NO-CO Reaction Cycle by Gold and Nickel Elucidated using a Well-Defined Model Bimetallic Catalyst Surface

“…Hollow NO peaks were observed at ∼1550 cm –1 . At the saturation coverage, hollow NO molecules that form a c(4 × 2)-2NO structure (θ NO = 0.5 ML) were observed at 1596 cm –1 . , The NO molecules adsorbed only on the hollow sites of Ni(111), unlike that observed for CO/Ni(111). ,− Figure b shows the IRAS spectra of NO on Au/Ni(111) as a function of exposure. The hollow NO peak was observed at ∼1550 cm –1 , but the peak intensity was smaller than that on Ni(111).…”