Strong-field approximation for ionization of a diatomic molecule by a strong laser field.III. High-order above-threshold ionization by an elliptically polarized field

摘要

We investigate high-order above-threshold ionization (HATI) of diatomic molecules having different sym-metries by an elliptically polarized laser field using the modified molecular strong-field approximation. Theyields of high-energy electrons contributing to the plateau region of the photoelectron spectra strongly dependon the employed ellipticity. This is more pronounced if the major axis of the polarization ellipse is parallel orperpendicular to the molecular axis and at the end of the high-energy plateau. For the 02 molecule (charac-terized by 7rg symmetry) the maximum yield is observed for some value of the ellipticity e different from zero.On the other hand, in the same circumstances, the N2 molecule (o-g) behaves as an atom, i.e., the yield ismaximum for 8.0. These characteristics of the photoelectron spectra remain valid in a wide region of themolecular orientations and laser peak intensities. The symmetry properties of the molecular HATI spectra areconsidered in detail: by changing the molecular orientation one or other type of the symmetry emerges ordisappears. Presenting differential ionization spectra in the ionized electron energy-emission angle plane wehave observed similar interference effects as in the HATI spectra governed by a linearly polarized field.