Berlin 2014 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 8: Electronic Spectroscopy 1
MO 8.3: Vortrag
Dienstag, 18. März 2014, 14:45–15:00, BEBEL HS213
Molecular Electronic Imaging via Laser Tunnelling — •Christopher T L Smeenk1, Ladan Arissian2, Alexei V Sokolov3, Kevin F Lee1,3, Michael Spanner1, Andre Staudte1, David M Villeneuve1, and Paul B Corkum1 — 1Joint Lab for Attosecond Science, Ottawa, Canada — 2University of New Mexico, Albuquerque, USA — 3Texas A & M University, College Station, USA
Photoionization by intense, infrared laser pulses occurs via a tunnelling process. The photo-electrons emitted in laser tunnelling provide insight into atomic and molecular orbitals, much in the same way that the tunnelling current in a scanning tunnelling microscope (STM) gives information about surfaces. Laser STM therefore provides an avenue to unite the Ångstrom scale spatial resolution of tunnelling with femtosecond temporal resolution of optical pulses, allowing for new kinds of microscopy on the sub-atomic length and time scales.
We use circularly polarized femtosecond laser pulses at 800 nm to control and image N2, O2, and benzene. A non-resonant pump laser pulse prepares a rotational wavepacket allowing us to align the molecular axis in the lab frame. A precisely timed probe pulse singly ionizes the aligned molecules. By recording the emitted photo-electron spectrum in the molecular frame of reference, we show how laser tunnelling probes the symmetry and local electron density in the highest-occupied-molecular-orbital. Our results on these prototypical Σ and Π bonded molecules suggest how a laser STM could be applied to image dynamics on the sub-atomic scale.