Prize Talk: Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics. Talk Title: X-ray laser probing of ultrafast surface catalysis and the anomalous properties of water*

I will demonstrate how x-ray lasers, such as LCLS at the SLAC National Accelerator Laboratory and PAL in Korea, are used to address basic scientific questions in chemical Physics. The first example will illustrate that we can observe surface catalytic reactions in real time using optical pump- x-ray-probe techniques. It has allowed for the detection of transient reaction intermediates in CO desrorption and for probing configurations close to the transition state during CO oxidation both on Ruthenium.

The second example will illustrate how it is now possible to probe water in the deep supercooled regime, where ice crystallization occurs rapidly. Using x-ray laser scattering on ultrafast timescales important features in the behavior of supercooled water could be revealed related to the existence of a liquid-liquid transition around 200 K and 1-2 kbar, and that the thermodynamic response function shows maxima at 230 K and 1 bar. Both observations are only consistent with the existence of a liquid-liquid critical point in deep supercooled water. Such a critical point cause fluctuations extending all the way up to ambient conditions and thereby points to the origin of waters anomalous properties.