Measuring the complex recombination dipole of aligned CO2 molecules in high-order harmonic generation

We generate high order harmonics in aligned CO2 molecules and measure the spectral amplitudes and phases as a function of the alignment angle. We control the quantum interference occurring in the recombination of an ultrafast laser-driven electron wavepacket with the highest occupied molecular orbital of CO2. By comparing to the emission of the reference system krypton , we obtain an experimental measure of the complex recombination dipole matrix element between the CO2 HOMO and a continuum state. The measured phase jump contains signatures of Coulombic wavepacket distortion .