Elementally Resolved Imaging of Dynamic Surface Processes: Chemical Waves in the SystemRh(110)/NO+H2

Spectromicroscopy of pulses transporting alkali metal in a surface reaction

“…The two N 1s components can be assigned to two different nitrogen species: chemisorbed nitrogen in the (2 Â 1)-N phase and nitrogen coadsorbed with oxygen in the mixed c(2 Â 4)-2O,N phase. 18,24,25 In the literature, the N 1s binding energy for the (3 Â 1)-N phase on Rh(110) (similar to the (2 Â 1)-N phase) is reported to be 397.3 eV and the one corresponding to the mixed c(2 Â 4)-NO coadsorbate phase equals 397.6 eV. 27 The separation of 0.3 eV is exactly the one we observe in the experiment.…”

“…The excitation cycle has been demonstrated using mXPS, mLEED, and via dark-field imaging of pulses in LEEM. 17,18,24,25 With coadsorbed potassium, the excitation cycle remains basically intact but one should expect that the potassium forms a coadsorbate phase with oxygen in a similar way as it was observed in Rh(110)/K/O 2 + H 2 . 20,26 Different phases within the pulse train on the K-promoted surface were identified by mLEED and mXPS under pattern forming reaction conditions.…”

“…24,25 The only significant modification with respect to the original mechanism is that the pure oxygen phase, the c(2 Â 6)-O, has to be replaced as the resting state by a K + O coadsorbate phase. The modified excitation cycle comprises the following sequence: K + O-coadsorbate phase (resting state) -(2 Â 1)-N (excited state) -c(2 Â 4)-2O,N (refractory state) -K + O coadsorbate phase.…”

Imaging with Chemical Analysis: Adsorbed Structures Formed during Surface Chemical Reactions

“…[17] PEEM, SPEM and LEEM have provided extensive knowledge about the spatiotemporal organisation of adspecies in these simple reaction-diffusion systems. [18][19][20][21][22][23] In these reactions, the reactants adsorb dissociatively on the Rh surface and the interaction between adsorbed H, O and N atoms leads to H 2 O or H 2 O + N 2 products, immediately desorbing in the gas phase. Under appropriate conditions, the adsorbates form stationary or moving two-dimensional concentration patterns, which also induce reversible structural transformations of the substrate.…”

“…Under appropriate conditions, the adsorbates form stationary or moving two-dimensional concentration patterns, which also induce reversible structural transformations of the substrate. [19][20][21] The water formation reaction on RhA C H T U N G T R E N N U N G (110) is bistable and the propagation of reaction fronts induce transitions between the O-covered ("oxidised") and clean ("reduced") surface. The oxygen adatoms react with hydrogen adatoms at the transition of the reduction front.…”