Wavelength and Polarization Effects in Strong-field Ionization of Diatomic Molecules Driven by Mid-infrared Laser Pulses

Abstract

The tunable long wavelength lasers with durations below 30 fs and focusable peak intensities around 1014 W/cm2 provide an important parameter to control the the ionization process of molecules with structural complexity and multi-core nature, which can explore the potential applications such as imaging the molecular orbitals and probing nuclear dynamics with attosecond resolution. In this paper, experimental and theoretical investigations of the ionization of homo-nuclear diatomic molecules (i.e., O 2 and N 2 ) radiated by both linearly polarized (LP) and circularly polarized (CP) mid-infrared laser fields are reported. We find the ionization yields of O 2 exhibit an apparent gap between different wavelengths in LP fields, while the yield-gap becomes obscure in CP fields. In particular, the dependence of the yield-gap of N 2 between different wavelengths on the laser polarization is in contrast to that of O 2 . With the help of the S-matrix theory, the peculiar polarization-dependent yield-gaps can be attributed to both the molecular orbital and the two-center interference effect in molecular ionization process. Our findings provide a new insight into the molecular ionization process and retrieving the information of the molecular structure.