Hannover 2013 – scientific programme
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A: Fachverband Atomphysik
A 9: Interaction with strong or short laser pulses I
A 9.4: Talk
Monday, March 18, 2013, 17:30–17:45, B 305
Adiabatic versus nonadiabatic effects in tunneling ionization of atoms — •Antonia Karamatskou1,2, Stefan Pabst1,2, and Robin Santra1,2 — 1Center for Free-Electron Laser Science, DESY, Hamburg, Germany — 2Department of Physics, University of Hamburg, Hamburg, Germany
We discuss the tunneling regime of atoms in a strong laser field within the framework of the adiabatic representation. This representation is commonly used in the field of molecular dynamics, where the motion of the nuclei is assumed to be so slow compared to the electronic motion that it justifies the usage of the Born-Oppenheimer approximation. This yields discrete potential energy curves of the system that are connected by nonadiabatic transitions. Here, we extend this method to the treatment of the strong-field ionization of atoms. By adding a complex absorbing potential the Hamiltonian becomes non-Hermitian. In this way, we obtain discrete eigenstates and the associated complex eigenvalues contain the physical tunneling rates. Via the full diagonalization of the instantaneous Hamiltonian we are able to observe the transition from the adiabatic regime to the region where nonadiabatic transitions become significant for the ionization. In our study we also clarify the impact of few-cycle pulses on the tunneling behavior. Thereby we refine the language employed for nonadiabaticity in strong field physics. Furthermore, we analyze the usage of the Keldysh parameter as an adiabaticity parameter for strong field ionization.