The influence of steps on the desorption kinetics of NO from Pt(111)

Abstract

A kinetic model is presented which describes thermal desorption of molecules from surfaces and incorporates trapping at steps. The model is applied to desorption of NO from Pt(111). The results of three molecular beam experiments, which differ substantially from each other, are accounted for quantitatively by the model using one set of rate parameters. It is demonstrated that steps, even when present in small concentrations on accurately cut crystals, can play a dominant role in thermal desorption. The magnitude of the effect depends on the difference between the binding energies on the terrace and at steps, which for NO on Pt(111) is large (25±2 kcal/mol and 34±2 kcal/mol, respectively). Furthermore, it is shown that the rate parameters governing terrace desorption, escape from steps, and surface diffusion can all be extracted from modulated molecular beam studies carried out for a suitable range of conditions.

Calculation of desorption rates for Xe/Pt(111) using a realistic gas–surface potential

“…Such an argument was given by Dresser, Madey, and Yates l4 to qualitatively explain the large (_1015 s -I) preexponentials they inferred for Xe desorption from W ( 111 ) based on TPD measurements. Related discussions of the kinetics of NO desorption from stepped Pt surfaces have been given by Serri et al,15,16 and by Kruse et al 17 Finally, we note that with the relationships ()d = nd1d andnd = (n -n,),Eq. (14) leads to an explicit formula for n, valid for arbitrary T and total Xe densities both larger or smaller than the defect density,…”

“…The value ofEq. (16) is that it allows the transition from the ideal surface to the defect dominated desorption regimes to be described analytically, so that processes such as TPD or isothermal desorption which involve this transition can be modeled.…”

Generation of ultra-short hydrogen atom pulses by bunch-compression photolysis

“…Further shortening is possible with smaller f/number optics, but requires reducing the photolysis volume further along the laser propagation direction. In Supplementary Note 1, we show that the spatial frequency distribution produced by the grating/lens combinationSupplementary Equation (19)-deviates from the ideal distribution, given by Supplementary Equation (15). See also Supplementary Fig.…”

“…See for example, ref. 12), time-resolved studies of surface adsorbate equilibration 13 as well as real-time kinetics of thermal desorption from terraces and steps 14,15 . Synchronized scattering of ultra-short matter pulses from photo-excited surfaces is another opportunity.…”

Kinetische Untersuchungen zur Pt‐katalysierten Oxidation von NO: Modellierung und Simulation

“…G R O T E et al [10] berichten von Desorptionsenergien an Pt(111) von 104,6 kJ/mol sowie an Pt(100) von 150,6 kJ/mol. Für die NO-Desorption an Stufen werden in der Literatur 142,3 kJ/mol angegeben [11]. Bei Untersuchungen an Pt/Al 2 O 3 werden Aktivierungsenergien von 145 kJ/mol gefunden [12].…”