1 The kinetics of elementary thermal reactions in heterogene- 2 ous catalysis 3 G. Barratt Park1,2, Theofanis Kitsopoulos2,5,6, Dmitriy Borodin1, Kai Golibrzuch2, Jannis 4 Neugebohren1, Daniel J. Auerbach2, Charles T. Campbell4 & Alec M. Wodtke1,2,3* 5 1Institute for Physical Chemistry, Georg-August University of Goettingen, Tammannstraße 6, 6 37077 Göttingen, Germany. 7 2Department of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Am 8 Faßberg 11, 37077 Göttingen, Germany. 9 3International Center for Advanced Studies of Energy Conversion, Georg-August University 10 of Goettingen, Tammannstraße 6, 37077 Göttingen, Germany. 11 4 Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA 12 5 Department of Chemistry, University of Crete, Heraklion, Greece 13 6 Institute of Electronic Structure and Laser – FORTH, Heraklion, Greece 14 15 *email:
[email protected] 16 17 KEYWORDS: Ion-imaging, velocity-resolved kinetics, CO oxidation, heterogeneous catalysis, 18 slice ion-imaging, molecular beams, surface chemistry. 19 20 1 21 Abstract 22 The kinetics of elementary reactions is fundamental to our understanding of catalysis. Just as 23 micro-kinetic models of atmospheric chemistry provided the predictive power that led to the 24 Montreal protocol reversing loss of stratospheric ozone, pursuing a micro-kinetic approach to 25 heterogeneous catalysis has tremendous potential for societal impact. However, developing this 26 approach for catalysis faces great challenges. Methods for measuring rate constants are quite 27 limited and present predictive theoretical methods remain largely un-validated. This paper pre- 28 sents a short perspective on recent experimental advances in our ability to measure the rates of 29 elementary reactions at surfaces that rely on a stroboscopic pump-probe concept for neutral 30 matter.