Dissociation and ionization of diatomic molecules in laser fields - full dimensional ab-initio description including electron-nuclear correlations

• Applicant: Professor Dr. Rüdiger Schmidt (†)
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280059503

The concern of this project is the extension of the recently developed "Non-Adiabatic Quantum Molecular Dynamics with Hopping" (NA-QMD-H) method to explicitly include an external laser field in the theoretical description during the molecular dynamics in harmonic, arbitrary long pulses. The new approach allows for an full-dimensional (including rotation, vibration, and electronic excitation) simultaneous ab-initio description of the laser-driven dissociation and ionization of two-atomic molecules, including quantum effects in the nuclear dynamics. This approach therefore is an approximative solution of the full time-dependend Schrödinger equation for electrons and nuclei. It is the ultimate goal of many years of development of Dresden's NA-QMD method (see Section "Eigene Vorarbeiten"). This goal shall be achieved with an approximate quantum-mechanical treatment of the nuclei, where classical trajectories are propagated on quantum-mechanically determined energy surfaces. The choice of these surfaces is crucical. In the intended method, Floquet surfaces (during the pulse) and Born-Oppenheimer surfaces (for the relaxation dynamics following the pulse) will be applied. In connection with quantum-mechanically determined transition rates between single surfaces ("hopping"), this should allow for an accurate description of the laser-driven molecular dynamics including electron-nuclear correlations. For H2+, we already have experience with this approach. The challenging extension of the method to two-atomic multi-electron molecules is the narrower concern of the present project. For the first time, density-functional-theory-Floquet surfaces of the Kohn-Sham system corresponding to the molecule shall be used here. A further new and important point of the method is the description of photoionization by hopping between surfaces of the neutral, single, or multiple ionized molecule, such that a complete description of all (relevant) ionization channels should be possible.For this project a cooperation agreement with the Max-Planck-Institut für Kernphysik (MPIK) Heidelberg has been concluded (see attachments). At the MPIK, kinematically complete experiments concerning the dissociation and ionization are performed using a reaction microscope. In consultation with the MPIK, specific calculations shall be done at first for argon dimers (later also for other noble gases as well as O2 and N2), the results shall be compared to the experimental findings and help with their interpretation. Furthermore, simulations for the interpretation of pump-probe experiments are planned. The new method allows for an explicit inclusion of the pump and the probe pulse in the calculation. A common aim, among others, is to investigate to what extent the molecular dynamics can be manipulated by suitable choices of the laser parameters.

• DFG Programme: Research Grants
• Cooperation Partner: Privatdozent Dr. Robert Moshammer