Westfälische Wilhelms-Universität Münster

- Fachbereich Physik -

 

KOLLOQUIUM ÜBER SPEZIELLE FRAGEN DER PHYSIK

 

 

Montag, 27. Mai 2002

 

 

Prof. Dr. G.J. Kroes

Institute of Chemistry, Leiden University

 

 

Vibrational effects on dissociative chemisorption of hydrogen:
6D quantum dynamics results for Cu(100) and Pt(111)

 

 

Computational results will be presented on the scattering of H2 from Cu(100) and Pt(111). The calculations are based on potential energy surfaces (PESs) computed with density functional theory (DFT). These are used in time-dependent wave packet calculations treating all six molecular degrees of freedom of H2  quantum mechanically.

In the calculations on H2 + Cu(100), a new analysis technique has been used to compute where in the surface unit cell the molecule reacts. The calculations predict that vibrationally excited (v=1) H2 reacts at the top site, which has a higher barrier than the lowest barrier bridge site at which (v=0) H2 reacts. Two ways in which this prediction can be confirmed in experiments will be discussed in the talk.

The issue addressed for H2 + Pt(111) is why calculations predict the reaction to be vibrationally enhanced, whereas experiments find no effect of exciting the vibration. Because the force constant of H2  decreases as it approaches the early barrier, v=1 H2  can release vibrational energy to overcome the barrier. The resulting vibrational enhancement cannot be observed in seeded beam experiments because v=0 H2 already dissociates at low energies on Pt(111).

 

 

Ort:      Wilhelm-Klemm-Str. 9, Hörsaal 404

Zeit:     17 Uhr c.t.

 

Einladender: Zacharias