X-ray induced electron and ion fragmentation dynamics in IBr.

Characterization of the inner-shell decay processes in molecules containing heavy elements is key to understanding x-ray damage of molecules and materials and for medical applications with Auger-electron-emitting radionuclides. The 1s hole states of heavy atoms can be produced by absorption of tunable x rays and the resulting vacancy decays characterized by recording emitted photons, electrons, and ions. The 1s hole states in heavy elements have large x-ray fluorescence yields that transfer the hole to intermediate electron shells that then decay by sequential Auger-electron transitions that increase the ion's charge state until the final state is reached.

Pink-beam focusing with a one-dimensional compound refractive lens.

The performance of a cooled Be compound refractive lens (CRL) has been tested at the Advanced Photon Source (APS) to enable vertical focusing of the pink beam and permit the X-ray beam to spatially overlap with an 80 µm-high low-density plasma that simulates astrophysical environments. Focusing the fundamental harmonics of an insertion device white beam increases the APS power density; here, a power density as high as 500 W mm(-2) was calculated. A CRL is chromatic so it does not efficiently focus X-rays whose energies are above the fundamental.

Feasibility of Valence-to-Core X-ray Emission Spectroscopy for Tracking Transient Species.

X-ray spectroscopies, when combined in laser-pump, X-ray-probe measurement schemes, can be powerful tools for tracking the electronic and geometric structural changes that occur during the course of a photoinitiated chemical reaction. X-ray absorption spectroscopy (XAS) is considered an established technique for such measurements, and X-ray emission spectroscopy (XES) of the strongest core-to-core emission lines (Kα and Kβ) is now being utilized. Flux demanding valence-to-core XES promises to be an important addition to the time-resolved spectroscopic toolkit.

Development of high-repetition-rate laser pump/x-ray probe methodologies for synchrotron facilities.

We describe our implementation of a high repetition rate (54 kHz-6.5 MHz), high power (>10 W), laser system at the 7ID beamline at the Advanced Photon Source for laser pump/x-ray probe studies of optically driven molecular processes. Laser pulses at 1.