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Tuesday, 26 October 2010

JC: Sebastien: Mapping Molecular Orbital Symmetriy on High-Order Harmonic Generation Spectrum Using Two-Color Laser Fields

We have measured high-order harmonic generation spectra of D2, N2, and CO2 by mixing orthogonally polarized 800 and 400 nm laser fields. The intensity of the high-harmonic spectrum is modulated as we change the relative phase of the two pulses. For randomly orientated molecules, the phase of the intensity modulation depends on the symmetry of the molecular orbitals from which the high harmonics are emitted. This allows us to identify the symmetry of any orbital that contributes to high-harmonic generation, even without aligning the molecule. Our approach can be a route to imaging dynamical changes in three-dimensional molecular orbitals on a time scale as short as a few hundred attoseconds.

Tuesday, 19 October 2010

DM: Chris Arrell: Thesis and Surface Science Experiments Outlook

I will present measurements from the surface science apparatus and discuss the next steps for the project. Measurements have shown evidence of localised plasmonic enhancement from silver and 'hot-electron' temporal dynamics on an Au surface

Tuesday, 12 October 2010

JC: Richard: Inconsistencies between two attosecond pulse metrology methods: A comparative study

The two basic approaches underlying most of the metrology of attosecond pulse trains are compared in the spectral region ~14-24 eV, that is, the second-order intensity volume autocorrelation and the resolution of attosecond beating by interference of two photon transitions (RABITT). They give rather dissimilar pulse durations. It is concluded that for the present experimental conditions RABITT may underestimate the duration under measurement, due to variations of the driving intensity, but in conjunction with theory allows an estimation of the relative contributions of two different electron trajectories to the extreme-ultraviolet (XUV) radiation.
PPT slides...

Tuesday, 5 October 2010

DM: Ryan: Tunneling discussion which directly measures tunneling in a strong field. I may also speak about: which claims to have measured tunneling time I will speak about that and offer a `tutorial' of sorts on tunneling covering the main features of tunneling and the basic theories behind that and the 3-step model. It will be a discussion of the paper coupled with a short lesson on the stuff that I am most often asked about by dirty experimentalists.
If there are specific things people want to know send Ryan an email.