Precise Access to the Molecular-Frame Complex Recombination Dipole through High-Harmonic Spectroscopy

Abstract : We report on spectral intensity and group delay measurements of the highest-occupied molecular-orbital (HOMO) recombination dipole moment of N2 in the molecular-frame using high harmonic spectroscopy. We take advantage of the long-wavelength 1.3 μm driving laser to isolate the HOMO in the near threshold region, 19–67 eV. The precision of our group delay measurements reveals previously unseen angleresolved spectral features associated with autoionizing resonances, and allows quantitative comparison with cutting-edge correlated 8-channel photoionization dipole moment calculations.