Combining ultrafast laser and x-ray spectroscopies for new insights into molecular dynamics

Laser and X-ray spectroscopic methods are both frequently used to elucidate structure and bonding in matter. We aim at developing and applying methods where we use a laser pulse to excite atoms and molecules in the gas phase, in liquids and in solids and where we interrogate the evolution of the system with ultrafast X-ray spectroscopic methods. Two examples will be discussed. First, our results on the ultrafast dissociation of Br₂ molecules in the gas phase with femtosecond photoelectron spectroscopy will be presented. We use high-order harmonic generation of an ultrafast Ti:Sa laser (800 nm) to produce our femtosecond VUV photon pulses with a photon energy of around 20 eV. Second, a novel infrared pump-X-ray probe technique is used to unravel structural dynamics in liquid water. A femtosecond Ti:Sa laser system is used to drive an optical parametric amplifier to generate intense infrared pulses and the X-ray probe pulses are generated in a soft X-ray undulator beamline at the synchrotron radiation source BESSYII.