Signatures of molecular structure in the strong-field response of aligned molecules

The strong-field response of molecules exhibits interference effects due to the geometric and electronic structure of the molecules and provides a basis for ultrafast imaging of molecular structure. This is demonstrated for high-order harmonic generation and high-order above-threshold ionization in aligned molecules by numerical solution of the time-dependent Schrodinger equation. Experimental and theoretical results for high-order harmonic generation with aligned CO2 molecules show that the harmonics exhibit an orientation dependence that is explained by the valence orbital symmetry. A detailed discussion of phase-matching effects due to the presence of different molecular orientations in an ensemble of imperfectly aligned molecules is presented.