NSLS-II Seminar

Structural changes of molecular systems triggered by electronic excitations play an important role for the functionality of biological systems, light-harvesting chemical systems and, last but not least, in the rational design of synthetic structures mimicking biological systems which convert chemical energy to motion. Pulsed X-ray sources such as storage rings provide a new stroboscopic tool, often complementary to laser-based techniques, to probe not only the electronic excitations but also the structural response of molecules. Some examples of laser-initiated X-ray spectroscopy and wide angle x-ray scattering will demonstrate the strength of these techniques which presently find its limitations due to limited photon flux and time-resolution. Alternative detection mechanisms, including optoelectronic techniques, and improved beamline concepts will be presented which have the potential to overcome these obstacles resulting in time resolution of about 1ps. The talk will show how the objectives of the user community and the mandate of the funding agencies are correlated with these technical and programmatic developments.