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.
http://prl.aps.org/abstract/PRL/v105/i5/e053003
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Tuesday, 26 October 2010
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.
http://pra.aps.org/abstract/PRA/v82/i2/e021402
PPT slides...
http://pra.aps.org/abstract/PRA/v82/i2/e021402
PPT slides...
Tuesday, 5 October 2010
DM: Ryan: Tunneling discussion
http://prl.aps.org/abstract/PRL/v105/i13/e133002
which directly measures tunneling in a strong field.
I may also speak about:
http://www.nature.com/nphys/journal/v4/n7/full/nphys982.html
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.
If there are specific things people want to know send Ryan an email.
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