Two-center interference and ellipticity in high-order harmonic generation fromH2+

Abstract

We present a theoretical investigation into the two-center interference in aligned H + 2 . The influence of the laser field on the recombination step is investigated by comparing laser-induced harmonic generation with harmonic generation from field-free collisions of Gaussian wave packets with the core. We find that for different Gaussian wave packets colliding with the molecule, the interference minimum occurs at the same alignment angle. The same result is obtained for the laser-induced spectrum when only a single electronic trajectory per harmonic contributes. When multiple electronic trajectories contribute, we find an effect on the minimum position because the interference between short and long trajectories is alignment dependent. The two-center interference and the influence of the Coulombic potential are clearly seen not only in the harmonic intensity and phase but also in the polarization direction and ellipticity. We observe significant ellipticity of the emitted radiation around the two-center interference minimum.

Laser-induced blurring of molecular structure information in high harmonic spectroscopy

“…This has two advantages: (i) we can easily achieve numerous computations both within the TDSE and the SFA framework, and implement analytical developments; (ii) we avoid additional effects like Coulomb refocusing or EWP spreading that was previously invoked to explain phase smoothing effects 21,22 . Note that we carried out preliminary 2D computations that are in overall agreement with our 1D results, eventhough they present extra features, that we plan to address in a forthcoming paper.…”

Spectrally resolved multi-channel contributions to the harmonic emission in N2

“…The second type, called 'structural', appears, e.g., when destructive interferences occur between XUV emissions from a two-center type of molecule [14,15]. Structural minima are characteristic of the recombination dipole moment (RDM) of a given channel and their positions do not change with the laser parameters [14,16], but they are sensitive to the molecular alignment angle θ with respect to the laser polarization [17][18][19]. The third type of minima, referred to as 'dynamical', is present when several molecular orbitals (channels) contribute to HHG.…”

Dynamical distortions of structural signatures in molecular high-order harmonic spectroscopy

“…This results in a discontinuous phase-jump of exactly ±π rad in the theoretical spectra. However, this behavior does not compare well with experimental data [51,53] nor with ab initio computations based on the exact resolution of the Time Dependent Schrödinger Equation (TDSE) [64,65,69]. The phasejumps at the destructive interferences are found far from being sharp: they are smoothed, cover several harmonics and span less than π rad.…”