Stuttgart 2012 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 1: Interaction with strong or short laser pulses I
A 1.2: Vortrag
Montag, 12. März 2012, 11:00–11:15, V55.01
Preparation and measurement of nuclear wave packets with ultrashort laser pulses: "Lochfraß" and the inversion motion of NH3 — •Johann Förster and Alejandro Saenz — Humboldt-Universität zu Berlin, Germany
Time-resolved imaging of the dynamics of electrons and nuclei is a prerequisite to understand chemical processes and, therefore, a great challenge for theory and experiment. Preparing and measuring nuclear wave packets describable within the promising pump-probe sheme "Lochfraß" was so far discussed theoretically [1] and experimentally [2] for diatomic molecules. The vibration of the molecule D2 was monitored experimentally with subfemtosecond and sub-Ångstrom resolution in real time. This became possible using two identical but delayed intense ultrashort laser pulses. While so far only diatomic molecules were considered, the Lochfraß effect should be observable for larger molecules as well. The challenge for theory consists in describing this higher dimensional coupled vibrational problem and suggesting pulse parameters for the experiment. For NH3, we expect a significant Lochfraß effect which can be understood within a simple one-dimensional double-well picture describing the inversion motion of the molecule. In addition to Lochfraß itself, also the tunneling problem in the double-well potential is of interest since a coordinate-dependent ionization rate allows the study of the wave packet traversing the inversion barrier, and thus to investigate quantum-mechanical tunneling.
[1] Goll et al., Phys. Rev. Lett. 97, 103003 (2006).
[2] Ergler et al., Phys. Rev. Lett. 97, 103004 (2006).