Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 3: Focus Session: Interactions of Molecules with Dielectric Surfaces

DF 3.4: Topical Talk

Montag, 23. März 2009, 15:45–16:05, WIL A317

Accurate Energetics of Ground and Excited States of Molecules on Surfaces — •Thorsten Klüner — Universität Oldenburg, Theoretische Chemie, 26111 Oldenburg

Photodesorption of small molecules from surfaces is one of the most fundamental processes in surface photochemistry. Despite its apparent simplicity, a microscopic understanding beyond a qualitative picture still poses a true challenge for theory. While the dynamics of nuclear motion can be treated on various levels of sophistication, all approaches suffer from the lack of sufficiently accurate potential energy surfaces, in particular for electronically excited states involved in the desorption scenario.

In the last decade, we have developed a systematic and accurate methodology to reliably calculate accurate ground and excited state potential energy surfaces (PES) for different adsorbate-substrate systems. These potential energy surfaces serve as a prerequisite for subsequent quantum dynamical wave packet calculations, which allow for a direct simulation of experimentally observable quantities such as velocity distributions.

In this contribution, I will focus on recent results obtained for photodesorption of NO and CO from a NiO(100) surface. In contrast to previous studies, we were able to construct highly accurate potential energy surfaces based on correlated quantum chemical calculations (CASPT-2/CCSD(T)). These potential energy surfaces were used in subsequent wave packet studies which reveal new desorption mechanisms. All results are in good agreement with recent experiments.