  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.

Atomic Physics;Optics