Tuesday, 28 April 2015
In the ‘attosecond lab’ we can now generate synchronised attosecond pulses at 20eV and 90eV, which we hope to use to make time resolved measurements of ultrafast electronic processes in atoms and molecules, such as charge migration. In conjunction, a new electron-ion particle detector has been installed (the ‘VMI-TOF’) in order to be able to get as much information as possible from the probe step in a ‘pump-probe’ measurement. I will try to give a brief overview of the theory of charge migration (from a non-theorist stand point!) and the challenges of making attosecond pump - attosecond probe measurements. I will then discuss the experimental implementation of spLEAD (single photon Laser Enabled Auger Decay) , a scheme to measure electron dynamics in the glycine molecule, and the operation of the VMI-TOF, with a view to informing future experiments .
Tuesday, 21 April 2015
Christian: JC: Efficient generation of below-threshold harmonics for high-fidelity multi- photon physics in the VUV spectral range
We demonstrate the generation of microjoule level, sub-20-fs, Ti:Sa fifth-harmonic pulses utilizing a loose-focusing geometry in a long Ar gas cell. The VUV pulses centered at 161.8 nm reach pulse energies of 1.1 μJ per pulse, while the corresponding pulse duration is measured with a second-order, fringe-resolved autocorrelation scheme to be 18±1 fs . Nonresonant, two-photon ionization of Kr and three-photon ionization of Ne verify the fifth-harmonic pulse high-intensity content and indicate the feasibility of multi-photon VUV pump-VUV probe studies of ultrafast atomic and molecular dynamics.