Influence of large permanent dipoles on molecular orbital tomography

TL;DR

This paper studies how large permanent dipoles affect molecular orbital tomography via high-order harmonic generation, revealing challenges with one-side recollision and proposing a tailored laser pulse to improve orbital reconstruction accuracy.

Contribution

It introduces a method using a tailored driving pulse to control HHG and improve molecular orbital tomography in molecules with large permanent dipoles.

Findings

Modified ionization rates hinder one-side recollision with standard pulses.

Adding a weak low-frequency pulse restricts electron recollision to one side.

Successful orbital reconstruction requires projecting dipole matrix elements perpendicular to the dipole.

Abstract

The influence of large permanent dipoles on molecular orbital tomography via high-order harmonic generation (HHG) is investigated in this work. It is found that, owing to the modification of the angle-dependent ionization rate resulting from the Stark shift, the one-side-recollision condition for the tomographic imaging can not be satisfied even with the few-cycle driving pulses. To overcome this problem, we employ a tailored driving pulse by adding a weak low-frequency pulse to the few-cycle laser pulse to control the HHG process and the recollision of the continuum electrons are effectively restricted to only one side of the core. Then we carried out the orbital reconstruction in both the length and velocity forms. The results show that, the orbital structure can only be successfully reproduced by using the dipole matrix elements projected perpendicular to the permanent dipole in both forms.