/de/research/projects/2.2/topics/Topic 3/index.html
2.2 Strong-field Few-body Physics
Project coordinator(s): H. Rottke, F. Morales
"Probing molecular dynamics by strong field ionization"

 

Present key activities
 

Theory of time-resolved photoelectron holography: time resolving hole dynamics in molecules
O. Smirnova, M. Ivanov

After ionization induced by the IR laser field, the liberated electron oscillates in the field and can revisit the parent ion. The electron oscillation energy scales as Il2 where l is the laser wavelength and I is the laser intensity. Thus, strong-field ionization with mid-IR laser pulses offers unique possibility of achieving very high electron kinetic energy without using very high laser intensity. Scattering (diffraction) of the electron off the parent ion records information about the ion. High electron energy during scattering means that the electron provides sub-Angstrom-scale spatial resolution of the target. This information is mapped onto the electron spectra. Moreover, as the recollision energy is linked to the time of recollision, different energies in the electron spectra after the scattering are linked to different scattering times and hence yield excellent temporal resolution, typically better than 100 asec. One of our theory goals is to utilize this potential of combining spatial and temporal resolution.

 

Strong field ionization of atoms and molecules with IR and mid-IR pulses
A. Rouzée, A. Hundertmark, B. Schütte, T. Nguyen

We study the strong field ionization of atoms and molecules consecutive to the interaction with a strong IR or mid-IR (0.8 µm up to 10 µm) laser pulses. Ionization occurs either in the multi-photon regime or via field ionization where the electron tunnel through the lowered barrier by the action of the laser field. In the latter, the newly born electron can oscillates in the electric field and can come back to its parent ion leading to processes such as high harmonic generation, non-sequential double ionization or high order above threshold ionization. Elastic electron scattering on the ionic potential can lead to interference in the photoelectron angular distribution (PAD) due to the different possible paths for the electron to reach the detector at a given final drift momentum. Theses interferences imprint both structural and dynamical information and are at the basis of novel experimental approaches where atomic and molecular structure and their dynamics are probed simultaneously with Ångstrom scale spatial resolution and sub-fs temporal resolution.