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Seminar: "Next-Generation Photoionization/Imaging Techniques for Dynamics and Kinetics of Surface Reactions" (Lecture)

Tuesday 12 June 2018Add to my calendar
from 10:00
G. Barratt Park (Institute for Physical Chemistry, University of Gottingen, Germany)

dr. Barratt Park (Univ.Gottingen)Heterogeneous catalysis is one of the key technologies for sustainable living in the 21st century. Molecular beam-surface scattering experiments can reveal the fundamental molecular dynamics that underlie catalysis at surfaces. Two new techniques, both based on photoionization followed by imaging of the photoelectrons or ions, demonstrate significant advantages for the study of (1) the kinetics of elementary reaction steps at surfaces and (2) the dynamics of chiral molecule-surface interactions.

1. Velocity-resolved kinetics is an ion imaging technique capable of simultaneously measuring the desorption time and angle-resolved velocity of the products of a surface catalyzed reaction. The technique provides accurate measurement of product flux and achieves superior time resolution compared with previous techniques for measuring the overall turnover rate of surface reactions. We demonstrate the technique for CO oxidation on single crystal Pt surfaces, and we elucidate the site-specific reaction kinetics for the first time. A model is developed that independently describes the velocity-resolved reaction kinetics at both the Pt(111) surface (with 0.25% step density) and the Pt(332) surface (with 16% step density).

2. There is a huge drive to develop heterogeneous catalysts for asymmetric chiral synthesis, which motivates the development of chiral-sensitive spectroscopic techniques, capable of determining enantiomeric excess under UHV molecular beam scattering conditions. Arguably the most sensitive technique is Photoelectron Circular Dichroism (PECD), which measures the forward/backward asymmetry in photoelectrons that are emitted when a chiral molecule is photoionized by circularly polarized light. In a 2+1 Resonance-Enhanced Multiphoton Ionization (REMPI) experiment via the n=3 Rydberg states of fenchone, we demonstrate for the first time that this technique can be performed with nanosecond dye lasers, which brings down the cost by ~2 orders of magnitude. We investigate the dependence of the effect on the electronic and vibrational state used as the REMPI intermediate.

prof. Alex Khajetoorians & prof. Bas van de Meerakker