Frankfurt 2006 – wissenschaftliches Programm
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A: Atomphysik
A 23: Wechselwirkung mit starken Laserpulsen III: Moleküle
A 23.5: Vortrag
Freitag, 17. März 2006, 11:55–12:10, H6
Above-threshold ionization in stretched molecules — •Ciprian Chirila and Manfred Lein — Max Planck Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg
Above-threshold ionization (ATI) is studied in diatomics with large internuclear separations. We solve the time-dependent Schrödinger equation (TDSE) numerically for a one-dimensional H2+ molecular ion. The ATI spectra are highly accurate even for large photoelectron-energies and are obtained using a Crank-Nicolson method with high accuracy in both space and time, combined with the window-operator technique.
We show that for certain values of the internuclear separation, the ATI spectrum extends up to 50 Up, where Up is the ponderomotive potential of the electron in the laser field. This can be understood within a classical model including electron scattering: An electron is born in the continuum at one of the nuclei with zero initial kinetic energy and moves under the influence of the laser field only. During its motion, it can scatter from the two nuclei and then escape the interaction region. Plateaus extending beyond the corresponding cutoff-energies can be understood if one takes into account the electron starting with non-zero velocity and weights the trajectories by the instantaneous ionization rate at the time of birth of the electron.