Molecular desorption

In this manuscript we will first describe the characteristics of the temperature jumps and the resulting molecular desorption which can be produced by a laser pulse. We then describe how we have implemented FTMS as a detection method in these experiments and present our results on several adsorbate systems. 

Laser-Induced Temperature Jumps and Molecular Desorption... 

MOLECULAR DESORPTION FROM SOLID SURFACES LASER DIAGNOSTICS AND CHEMICAL DYNAMICS... 

The desorption flux is so low under these conditions that no gas phase collisions occurred between molecular desorption and LIF probing. Phase space treatments " of final-state distributions for dissociation processes where exit channel barriers do not complicate the ensuing dynamics often result in nominally thermal distributions. In the phase space treatment a loose transition state is assumed (e.g. one resembling the products) and the conserved quantities are total energy and angular momentum the probability of forming a particular flnal state of ( , J) is obtained by analyzing the number of ways to statistically distribute the available (E, J). 

Molecular Desorption from Solid Surfaces Laser Diagncbtics AND Chemical Dynamics 45... 

The existence of multiple peaks for molecular desorption has been attributed to lateral interactions among adsorbed species 62-64). As discussed previously, adsorption onto the surface lattice may occur preferentially in next nearest neighbor sites to form p(2 x 2) structures. Even at low coverages, attractive forces may cause adatoms to occupy next nearest neighbor positions, so that clusters of adsorbate form which have local twofold periodicity 65) with respect to the surface. Such effects are entirely consistent with the perturbations of the surface electronic wave functions due to adsorption 66-68) which show that these binding sites represent the... 

For molecular desorption, laser spectroscopic studies of the desorbing molecule can give full internal state distributions, Df Ef, 6f, v, J, f M ), Ts), where f M ) is some distribution function describing the rotational orientation/alignment relative to the surface normal. For thermal desorption in non-activated systems, most atoms/molecules have only modest (but important) deviations from a thermal distribution at Ts. However, in associative desorption of systems with a barrier, the internal state distributions reveal intimate details of the dynamics. Associative desorption results from the slow thermal creation of a transition state, with a final thermal fluctuation causing desorption. Partitioning of the energy stored in V into... 

Figure 24.7 Comparison of TDS results following the reaction of 1,3-butadiene on clean and carbide-modified V(110) surfaces. The left-panel shows the molecular desorption of 1,3-butadiene (major cracking pattern at 39 amu) and the right-panel shows the desorption of...

D. Beksic and D. A. Micha. Electronically diabatic quantum dynamics of molecular desorption. J. Chem. Phys., 103 3795, 1995. 

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