Femtosecond coincidence imaging of optimal control in chemical dynamics

The use of femtosecond laser pulse shaping is currently proliferating as a tool for the research on photodynamics of molecules. Complex pulses can be obtained by a Fourier-domain shaping technique with the use of a Liquid-Crystal Display (LCD). We will use the same device for polarization shaping of femtosecond laser pulses. The spectral phase modulation can be imposed independently onto two orthogonal polarization directions with a two-layer LCD, therefore giving rise
to time-varying polarization states in the laser pulse. The shaped pulses will be used to study and control photodynamics and photoionisation of molecules. The most complete information on such processes can be obtained with the photo-electron/photo-ion coincidence imaging technique. Coincidence imaging is a technique in which both the recoiling photo-electron and the correlated
ionic photofragment originating from isolated dissociation/ionisation events are detected. It generates three dimensional energy- and angle resolved images, which reveal the energy distribution over the different photofragments and correlations between them. With this information it is possible to extract the photo-electron angular distribution in the molecular frame. A change in this
distribution over time directly reflects the photodynamics of the system under investigation.
The new laboratory will integrate the pulse shaping with an advanced coincidence molecular beam apparatus to learn about mechanisms in optimal control of ultrafast chemical dynamics.

Contact: Maurice Janssen; e-mail: MHM.Janssen@few.vu.nl
Physical Chemistry

24Photo-electron/photoion coincidence imaging combined with laser pulse shaping.