Molecular Excited-State Structure by Time-Resolved Pump-Probe X-ray Diffraction. What Is New and What Are the Prospects for Further Progress?

Time-resolved diffraction by laser pump X-ray probe methods for the determination of the geometry of molecular excited states is discussed. A number of examples are presented and compared with theoretical results. The increasing brightness and time resolution of new light sources now becoming available will likely enable the tracking of dynamic processes in solids on femtosecond time scales.