Selective Production of Reactive and Nonreactive Oxygen Atoms on Pd(001) by Rotationally Aligned Oxygen Molecules

Abstract

Sticking together: The occupation of different sites by oxygen atoms that are produced by the dissociation of O(2) on Pd(100) is determined by the initial rotational alignment of the parent molecules. The atom locations are characterized by different chemical reactivities in the reaction with CO to form CO(2) (see picture), which are followed by synchrotron radiation (SR) experiments with a supersonic molecular beam (SMB).

Sticking Probability and Reactivity of Hyperthermal O2 Molecules Impinging on CO Pre-covered Pd(100): Effect of Rotational States with K > 1

“…The data for T N = RT (bottom panel) clearly indicates that even if the sticking probabilities are the same for ST and FT, the CO 2 yield is definitively higher when dosing with ST. This result, already reported in [15] was accounted for by the fact that FT, which consists of at least 67 % of cartwheels in our experimental setup, produces mainly nonreactive oxygen atoms while ST generates reactive O leading to CO 2 production. The minor CO 2 signal observed for FT is thereby compatible with the fraction of helicoptering molecules present in the FT beam.…”

“…In our previous investigations [14,15] of the stereodynamical effect in the adsorption and reaction of O 2 with CO pre-covered Pd(100) we established that:…”

“…Such direction becomes therefore the ''natural'' axis to define the spatial quantization of the final rotational states and to describe any beam scattering event far from the expansion zone. Stereodynamical effects in collisions have been investigated both in the gas phase [12] and at surfaces [13][14][15] by velocity selected SMB using a slotted disks mechanical device. The tails of the beam velocity distribution are thereby used for uptake experiments in which both the sticking probability and the reactivity with pre-adsorbed species can be directly measured.…”

Polar molecules engaged in pendular states captured by molecular-beam scattering experiments

“…The following collision dynamics can be affected by orientational effects at long range, * lz@fis.unb.br i.e., in the entrance channels of chemical reactions. Radial and angular dependencies of molecular interactions, driving the collision dynamics of reactants, have often been recognized as central to an understanding of reaction mechanisms in gas phase [24] and at surfaces [25][26][27][28]. These features turn out to be particularly relevant from the simple species of interest in our chemical environment and even in the interstellar medium (water, hydrogen, ammonia, carbon dioxide, atomic and molecular ions of various types, etc.)…”

Communication: Fully alignment-specified O2 chemisorption on vicinal Si(100)

“…Stereodynamics in O 2 -surface interaction is, however, still far from being properly understood despite its great technological importance in heterogeneous catalysis, corrosion, and semiconductor industry. Previous studies employing aligned O 2 beams prepared with collisional alignment [1][2][3] or magnetic hexapolar field [4][5][6] have unveiled steric effects in O 2 chemisorption on Si(100), 4 Al(111), 5 clean 1 and adsorbed Pd(100) 2 surfaces. All of them, however, concern the polar angle effect of the O 2 axis; i.e., the difference in O 2 reactivity between the cases of side-on and end-on collisions.…”