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Tuesday, 16 December 2014

Konstantin: DM: Probing controlled dynamics

In this week's Journal Club I will discuss a proposed scheme to use the interference between short and long trajectories in HHG, so called Quantum Path Interference (QPI), to probe sub-femtosecond hole dynamics. The TDSE for a model H2 molecule in an intense IR field and a weaker UV field (resonant with the ionic transition between HOMO and HOMO-2) is solved numerically (idea and calculations by Suren Sukiasyan et al.). The population transfer driven by the resonant UV field changes the recombination probabilities of the short and long trajectories, leading to a change in QPI contrast. I will then discuss how we plan to implement this and similar experiments in the lab.

Tuesday, 9 December 2014

Allan: JC: High-flux table-top soft x-ray source driven by sub-2-cycle, CEP stable, 1.85-μm 1-kHz pulses for carbon K-edge spectroscopy

We report on the first table-top high-flux source of coherent soft x-ray radiation up to 400 eV, operating at 1 kHz. This source covers the carbon K-edge with a beam brilliance of (4.3±1.2)×1015  photons/s/mm2/strad/10%bandwidth and a photon flux of (1.85±0.12)×107  photons/s/1% bandwidth. We use this source to demonstrate table-top x-ray near-edge fine-structure spectroscopy at the carbon K-edge of a polyimide foil and retrieve the specific absorption features corresponding to the binding orbitals of the carbon atoms in the foil.