Molecular imaging with circularly polarized strong fields

• Antragsteller: Professor Dr. Manfred Lein
• Fachliche Zuordnung: Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen
• Förderung: Förderung von 2012 bis 2017
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 229920682

The response of atoms and molecules to strong laser pulses is a challenge to theoretical physics and it is interesting for practical applications such as imaging of molecular structure on the Angstrom spatial scale and few-femtosecond to subfemtosecond time scale.In this project, we investigate the electron momentum distributions from ionization in circularly polarized fields with both numerical and analytical quantum mechanical methods. We answer a number of fundamental questions and examine the potential of this approach for ultrafast imaging. Circular polarization maps extremely short time scales in the attosecond range onto macroscopic emission angles of electrons. Besides the angular distributions of electrons, the other main observable is the lateral width of the distributions, i.e. the width in the direction perpendicular to the applied laser field. Judging from recent experimental and theoretical studies the lateral width is an easily interpretable quantity since it is well predictable by the theory of tunnel ionization. We investigate to what extent it carries information about molecular structure and how this information can be retrieved from the momentum distributions. Fundamental questions that we wish to answer include the dependence on the laser wavelength and the relevance of the lateral distribution for the recently discovered low-energy structure in the electron energy spectra from mid-infrared pulses. The relevance of contributions from multiple electronic orbitals to the total signal will be addressed. In a proof-of-principle calculation, we plan to show the possibility to resolve ultrafast molecular photodissociation by observing the momentum spectrum from ionization by a time-delayed circularly polarized pulse. Our theoretical methods include the numerical solution of the three-dimensional time-dependent Schrödinger equation and approximate models such as the strong-field approximation.

• DFG-Verfahren: Sachbeihilfen