Hamburg 2009 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 11: Attosecond Physics I
A 11.2: Fachvortrag
Dienstag, 3. März 2009, 14:30–15:00, VMP 6 HS-B
Multi-orbital effects for high harmonic generation in N2 — •Markus Gühr, Brian K. McFarland, Joseph P. Farrell, and Philip H. Bucksbaum — Stanford PULSE Institute, SLAC National Accelerator Lab, Menlo Park, CA 94025 and Physics Department, Stanford University, Stanford CA 94305, USA
High harmonic generation (HHG) proceeds in three steps. First, a part of the electron wave function tunnels out of the valence orbital. The liberated electron wave packet accelerates in the laser field and finally coherently recombines with the initially ionized orbital. This leads to emission of harmonics of the driving laser frequency. The harmonic spectrum contains information about the valence orbital [1]. For molecules, the highest occupied molecular orbital (HOMO) is generally thought to be responsible for ionization and recombination during HHG. Molecular electronic states energetically below the HOMO should contribute to HHG, but this behavior has not been observed previously. Utilizing molecular alignment, we obtain experimental evidence that the more deeply bound HOMO-1 with its πu symmetry also contributes to HHG in N2 [2]. Semi-classical simulations of the recombination process to the HOMO and HOMO-1 support our observation. This opens the route to imaging coherent superpositions of electronic orbitals.
J. Itatani et al., Nature 432, 867 (2004)
B. K. McFarland, J. P. Farrell, P. H. Bucksbaum and M. Gühr, Science 322, 1232 (2008)