Laser Induced Molecular Imaging
Monday, 10. March, 9:45 h, 1A
Molecular multiphoton ionization in the tunneling limit is similar to tunneling in a scanning tunneling microscope. In both cases an electron (or electron wave packet) escapes from the outer regions of the orbital to the continuum. However, in the case of multiphoton ionization, both the momentum of the electrons and the ions can be measured. As we rotate the molecule, the photoelectron spectrum samples filter projections of the momentum wave function of the ionizing orbital. Some electrons created during multiphoton ionization re-collide with their parent ion. The re-colliding electron can:
- Diffract, revealing the scattering potential of the ion. That is, revealing the molecular structure).
- Interfere with the initial orbital from which it separated creating attosecond XUV pulses or pulse trains. The amplitude and phase of the radiation contains all information needed to re-construct the image of the orbital (just as a sheared optical interferometer can fully characterize an optical pulse).
All of these methods and supported by experiment and are compatible with measuring dynamics. Thus, multiphoton ionization is providing an extensive range of new tools to apply to important atomic or molecular problems.
Paul Corkum
National Research Council of Canada, Ottawa, Ontario, Canada