Time resolved X ray absorption spectroscopy of infrared laser induced temperature jumps in liquid water

A time resolved X ray absorption study of the structural dynamics of liquid water on a picosecond timescale is presented. We apply femtosecond midinfrared pulses to resonantly excite the intramolecular O H stretching band of liquid water and monitor the transient response in the oxygen K edge absorption spectrum with picosecond X ray pulses. In this way, structural changes in the hydrogen bond network of liquid water upon an ultrafast temperature jump of approximately 20 K are investigated. The changes of the X ray absorption as induced by such a temperature jump are about 3.2 . This demonstrates that our method serves as a sensitive probe of transient structural changes in liquid water and that combined infrared laser synchrotron experiments with substantially shorter X ray pulses, such as generated with a femtosecond slicing scheme, are possibl

Magnetic dichroism in the 4f4f photoelectron spectra of free Eu atoms: Experimental proof of the atomic character of thin film Eu–Gd MCD

The 4f photoionization of Eu atoms oriented in the ground state was investigated by means of photoelectron spectroscopy with linearly polarized vacuum ultraviolet radiation. Strong magnetic dichroism could be observed for atoms oriented parallel/antiparallel to the VUV photon beam by optical pumping with circularly polarized laser radiation. The magnetic dichroism of the free atoms, well described within the general theory of photoelectron angular distribution, displays the same characteristic features as the CMD of thin Eu films on a ferromagnetic Gd substrate

Real Time Evolution of the Valence Electronic Structure in a Dissociating Molecule

Time resolved valence band photoelectron spectroscopy with a temporal resolution of 135 fs is used to map the entire occupied valence electronic structure of photoexcited gas phase Br 2 molecules during dissociation. The observed shifting and mixing of valence energy levels defines a transition period where the system appears to be intermediate between atoms and molecules. The surprisingly short bond breaking or dissociation time is determined by monitoring in real time how the photoelectron multiplet structure of the free atom arises from the valence states of the photoexcited molecul