Rotational Dynamics in Associative Desorption of Hydrogen from Pd(100) and Cu(111) Surfaces

Abstract

The rotational dynamics in associative desorption of hydrogen from an s‐metal and a transition metal surface is state‐selectively investigated by resonantly enhanced two‐photon ionization and by laser induced fluorescence. From these measurements rotational state populations, state‐selective velocity distributions, and the spatial alignment of the rotational angular momentum can be deduced. Recently, fully six‐dimensional potential energy surfaces (PES) have been developed for this reaction on both substrates which allow quantum mechanical simulations of the dynamics. First calculations provide a comparison with the experimental data. The different chemical nature of palladium and copper is reflected in the rotational state population, the coupling of rotation to other degrees of freedom, and the spatial alignment of the rotation. For Pd(100) good agreement between theory and experiment is obtained, while for Cu(111) the experimental data suggest that the azimuthal corrugation is significantly higher than assumed in the calculations.

Vibrational and rotational population distribution ofD2associatively desorbing from Pd(100)

“…22 Experimentally a large number of studies have been performed that focused either on the hydrogen dissociative adsorption on metal surfaces [23][24][25] or the recombinative desorption from these surfaces. [26][27][28][29] Note that adsorption and desorption are related through time-reversal symmetry. The initial dissociative sticking probability of H 2 on various Cu surfaces has been measured by molecular beam techniques.…”

Mechanism of the Poisoning Action Of Sulfur on Catalytically Active Pd(100)

“…C is proportional to the population in the initial state, and v denotes the angular momentum coupling factor, which can be obtained from Eqs. (8)- (12) in Ref. [11].…”

“…The geometrical factors e͑V͒ are tabulated for the present setup in Ref. [12]. The summation runs over all possible combinations of the multipole moments k a and k d of the absorbed and detected photons, respectively.…”

Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

“…Unfortunately, no azimuth-angle dependence has been found in the flux of desorbing hydrogen molecules in thermally activated 2H(a)→H 2 (g) on metal surfaces despite many attempts [23,24] and proposals [25]. In the energetics of this process, the structural information of reaction sites is missing [26,27].…”