Simulation of optical and X-ray sum frequency generation spectroscopy of one-dimensional molecular chain

The time-resolved sum frequency generation signal of an optical and X-ray pulse is calculated for a one-dimensional molecular chain. We show how the valence exciton motion induced by the first optical light pulse can be probed with atomic scale precision by tuning the X-ray frequency across a core excitation of a particular atom. This technique provides a novel real-time, real-space probe for dynamics of valence excitation in a single molecule. (C) 2004 Elsevier B.V. All rights reserved.