One of the main goals of attosecond science is to see how the electrons are "behaving" in a molecule and to have a control over the behavior.
Two-color HHG may provide a way to achieve both of the above listed aims at the same time. In N2 the energy separation of the HOMO and HOMO-1 corresponds to 1.4eV. Removing an electron from HOMO by tunnel ionization leaves an electronic hole there. Subsequently, irradiating the target with a pump beam, one may start a Rabi kind of population transfer between HOMO and HOMO-1. Depending on the excursion time of the electrons the different harmonic orders may find the HOMO orbital populated differently.
We expect that due to the population evolution of the HOMO electronic state the spectrum of the emitted harmonics will be altered.