Dressed states of the high-frequency Floquet theory for atoms and molecules with standard computational quantum chemistry programs

The multipole expansion of the electron-nucleus interaction in the so-called high-frequency limit of the Floquet theory in the Kramers-Henneberger frame is used to determine equivalent point-charge distributions. This allo vs the use of standard quantum chemistry programs to calculate the energies. It is found that satisfactory results can be obtained with a quadrupole approximation if the parameter alpha(0) = E-0 omega(-2) (E-0, amplitude of electric field; omega, frequency of the field) does not exceed 30 au. The tramples which are treated are the hydrogen atom, the hydrogen negative ion H- and the hydrogen molecular ion H-2(+), systems for which accurate results are available.