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The three-step model for high harmonic generation shows that the
spectrum emitted by aligned molecules is the product of the
angle-dependent ionization probability, the propagation of the electron
in the continuum, and the transition matrix element of the
recombination. Modelling the continuum wavefunction when it returns to
the parent ion as a plane wave makes the analysis simpler, and has been
shown to be a reasonable approximation for atoms and some molecules.
Most molecules have pi orbitals, which means that they have nodal planes at which the wavefunction vanishes. The plane wave approximation breaks down for this condition. We show experimentally that we can use elliptically polarized laser light to push the nodal plane away from the parent ion. Results for aligned N2 and CO2 will be shown. A model will be used to explain some of the results. |
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