Quantum interference and multielectron effects in high-harmonic spectra of polar molecules

We experimentally and theoretically analyze the manifestations of quantum interference and multiple ionization channels (multiple orbitals) in high-harmonic spectra of aligned N2O molecules. Increasing the probe wavelength from 1.17 to 1.46 mu m, we demonstrate the gradual disappearance of multielectron effects and quantitatively explain the observation through calculations. We thus identify a minimum in the high-harmonic spectrum of N2O caused only by its structure. By comparing its position with that measured in the isoelectronic CO2 molecule for similar axis distributions, we find a difference of 10 eV, confirmed by ab initio quantum scattering calculations. Quantum interference in photorecombination is thus shown to be sensitive to subtle differences in the valence orbital structure of molecules with nearly identical lengths. This property may find applications in time-resolved studies. DOI: 10.1103/PhysRevA.87.031401